CIS Ubuntu Linux 22.04 LTS Benchmark v3.0.0 - 10-30-2025 Internal Only - General Terms of Use Please see the below link for our current terms of use: https://www.cisecurity.org/cis-securesuite/cis-securesuite-membership-terms-of-use/ For information on referencing and/or citing CIS Benchmarks in 3rd party documentation (including using portions of Benchmark Recommendations) please contact CIS Legal (legalnotices@cisecurity.org) and request guidance on copyright usage. NOTE: It is NEVER acceptable to host a CIS Benchmark in ANY format (PDF, etc.) on a 3rd party (non-CIS owned) site. Page 1 Internal Only - General Table of Contents Terms of Use ................................................................................................................. 1 Table of Contents .......................................................................................................... 2 Overview ...................................................................................................................... 11 Important Usage Information ...............................................................................................11 Key Stakeholders ................................................................................................................................. 11 Apply the Correct Version of a Benchmark ...................................................................................... 12 Exceptions ............................................................................................................................................ 12 Remediation ......................................................................................................................................... 13 Summary ............................................................................................................................................... 13 Target Technology Details ...................................................................................................14 Intended Audience................................................................................................................14 Consensus Guidance ...........................................................................................................15 Typographical Conventions .................................................................................................16 Recommendation Definitions ..................................................................................... 17 Title ........................................................................................................................................17 Assessment Status...............................................................................................................17 Automated ............................................................................................................................................ 17 Manual ................................................................................................................................................... 17 Profile ....................................................................................................................................17 Description ............................................................................................................................17 Rationale Statement .............................................................................................................17 Impact Statement ..................................................................................................................18 Audit Procedure ....................................................................................................................18 Remediation Procedure........................................................................................................18 Default Value .........................................................................................................................18 References ............................................................................................................................18 CIS Critical Security Controls® (CIS Controls®) ..................................................................18 Additional Information..........................................................................................................18 Profile Definitions .................................................................................................................19 Acknowledgements ..............................................................................................................20 Recommendations ...................................................................................................... 21 1 Initial Setup ........................................................................................................................21 1.1 Filesystem ...................................................................................................................................... 21 1.1.1 Configure Filesystem Kernel Modules ................................................................................... 22 1.1.1.1 Ensure cramfs kernel module is not available (Automated) ......................................... 23 1.1.1.2 Ensure freevxfs kernel module is not available (Automated) ....................................... 26 Page 2 Internal Only - General 1.1.1.3 Ensure hfs kernel module is not available (Automated) ............................................... 29 1.1.1.4 Ensure hfsplus kernel module is not available (Automated) ........................................ 32 1.1.1.5 Ensure jffs2 kernel module is not available (Automated) ............................................. 35 1.1.1.6 Ensure overlay kernel module is not available (Automated) ........................................ 38 1.1.1.7 Ensure squashfs kernel module is not available (Automated) ..................................... 41 1.1.1.8 Ensure udf kernel module is not available (Automated) ............................................... 44 1.1.1.9 Ensure usb-storage kernel module is not available (Automated) ................................. 47 1.1.1.10 Ensure unused filesystems kernel modules are not available (Manual) .................... 51 1.1.1.11 Ensure firewire-core kernel module is not available (Automated) .............................. 58 1.1.2 Configure Filesystem Partitions ............................................................................................. 61 1.1.2.1 Configure /tmp .................................................................................................................... 62 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated) ......................................... 63 1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated) ............................................ 66 1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated) ........................................... 68 1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated) .......................................... 70 1.1.2.2 Configure /dev/shm ............................................................................................................ 72 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition (Automated) ................................. 73 1.1.2.2.2 Ensure nodev option set on /dev/shm partition (Automated) .................................... 75 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition (Automated) .................................... 77 1.1.2.2.4 Ensure noexec option set on /dev/shm partition (Automated) ................................... 79 1.1.2.3 Configure /home ................................................................................................................. 81 1.1.2.3.1 Ensure separate partition exists for /home (Automated) ........................................... 82 1.1.2.3.2 Ensure nodev option set on /home partition (Automated) ......................................... 84 1.1.2.3.3 Ensure nosuid option set on /home partition (Automated) ........................................ 86 1.1.2.4 Configure /var ..................................................................................................................... 88 1.1.2.4.1 Ensure separate partition exists for /var (Automated) ............................................... 89 1.1.2.4.2 Ensure nodev option set on /var partition (Automated) ............................................. 91 1.1.2.4.3 Ensure nosuid option set on /var partition (Automated) ............................................ 93 1.1.2.5 Configure /var/tmp .............................................................................................................. 95 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated) ........................................ 96 1.1.2.5.2 Ensure nodev option set on /var/tmp partition (Automated) ...................................... 98 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition (Automated) ................................... 100 1.1.2.5.4 Ensure noexec option set on /var/tmp partition (Automated) .................................. 102 1.1.2.6 Configure /var/log ............................................................................................................. 104 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated) ....................................... 105 1.1.2.6.2 Ensure nodev option set on /var/log partition (Automated) ..................................... 107 1.1.2.6.3 Ensure nosuid option set on /var/log partition (Automated) .................................... 109 1.1.2.6.4 Ensure noexec option set on /var/log partition (Automated) ................................... 111 1.1.2.7 Configure /var/log/audit ................................................................................................... 113 1.1.2.7.1 Ensure separate partition exists for /var/log/audit (Automated) .............................. 114 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition (Automated) ............................ 116 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition (Automated) ............................ 118 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition (Automated)........................... 120 1.2 Package Management ................................................................................................................. 122 1.2.1 Configure Package Repositories .......................................................................................... 123 1.2.1.1 Ensure GPG keys are configured (Manual) ................................................................ 124 1.2.1.2 Ensure package manager repositories are configured (Manual) ............................... 127 1.2.2 Configure Package Updates ................................................................................................. 129 1.2.2.1 Ensure updates, patches, and additional security software are installed (Manual) ... 130 1.3 Mandatory Access Control ......................................................................................................... 132 1.3.1 Configure AppArmor.............................................................................................................. 133 1.3.1.1 Ensure the apparmor packages are installed (Automated) ........................................ 134 1.3.1.2 Ensure AppArmor is enabled (Automated) ................................................................. 136 1.3.1.3 Ensure all AppArmor Profiles are not disabled (Automated) ...................................... 138 1.3.1.4 Ensure all AppArmor Profiles are enforcing (Automated) .......................................... 140 1.4 Configure Bootloader .................................................................................................................. 142 Page 3 Internal Only - General 1.4.1 Ensure bootloader password is set (Automated) ........................................................... 143 1.4.2 Ensure access to bootloader config is configured (Automated) .................................... 146 1.5 Configure Additional Process Hardening ................................................................................. 148 1.5.1 Ensure randomize_va_space is configured (Automated) .............................................. 149 1.5.2 Ensure ptrace_scope is configured (Automated) .......................................................... 154 1.5.3 Ensure suid_dumpable is configured (Automated)........................................................ 159 1.5.4 Ensure core file size is configured (Automated) ............................................................ 163 1.5.5 Ensure prelink is not installed (Automated) ................................................................... 165 1.5.6 Ensure Automatic Error Reporting is configured (Automated) ...................................... 166 1.6 Configure Command Line Warning Banners ............................................................................ 168 1.6.1 Ensure /etc/motd is configured (Automated) ................................................................. 169 1.6.2 Ensure /etc/issue is configured (Automated) ................................................................. 172 1.6.3 Ensure /etc/issue.net is configured (Automated) ........................................................... 174 1.6.4 Ensure access to /etc/motd is configured (Automated) ................................................. 176 1.6.5 Ensure access to /etc/issue is configured (Automated)................................................. 178 1.6.6 Ensure access to /etc/issue.net is configured (Automated) .......................................... 180 1.7 Configure GNOME Display Manager .......................................................................................... 182 1.7.1 Ensure GDM is removed (Automated) .......................................................................... 183 1.7.2 Ensure GDM login banner is configured (Automated) ................................................... 185 1.7.3 Ensure GDM disable-user-list option is enabled (Automated) ...................................... 188 1.7.4 Ensure GDM screen locks when the user is idle (Automated) ...................................... 191 1.7.5 Ensure GDM screen locks cannot be overridden (Automated) ..................................... 194 1.7.6 Ensure GDM automatic mounting of removable media is disabled (Automated) .......... 196 1.7.7 Ensure GDM disabling automatic mounting of removable media is not overridden (Automated) ............................................................................................................................ 198 1.7.8 Ensure GDM autorun-never is enabled (Automated) .................................................... 200 1.7.9 Ensure GDM autorun-never is not overridden (Automated) .......................................... 202 1.7.10 Ensure XDMCP is not enabled (Automated) ............................................................... 204 1.7.11 Ensure Xwayland is configured (Automated) .............................................................. 207 2 Services............................................................................................................................209 2.1 Configure Server Services .......................................................................................................... 210 2.1.1 Ensure autofs services are not in use (Automated) ....................................................... 211 2.1.2 Ensure avahi daemon services are not in use (Automated) .......................................... 214 2.1.3 Ensure dhcp server services are not in use (Automated).............................................. 217 2.1.4 Ensure dns server services are not in use (Automated)................................................ 220 2.1.5 Ensure dnsmasq services are not in use (Automated) .................................................. 222 2.1.6 Ensure ftp server services are not in use (Automated) ................................................. 224 2.1.7 Ensure ldap server services are not in use (Automated)............................................... 227 2.1.8 Ensure message access server services are not in use (Automated) .......................... 229 2.1.9 Ensure network file system services are not in use (Automated) .................................. 232 2.1.10 Ensure nis server services are not in use (Automated) ............................................... 234 2.1.11 Ensure print server services are not in use (Automated) ............................................ 237 2.1.12 Ensure rpcbind services are not in use (Automated)................................................... 240 2.1.13 Ensure rsync services are not in use (Automated) ...................................................... 243 2.1.14 Ensure samba file server services are not in use (Automated) ................................... 245 2.1.15 Ensure snmp services are not in use (Automated) ...................................................... 247 2.1.16 Ensure tftp server services are not in use (Automated) .............................................. 250 2.1.17 Ensure web proxy server services are not in use (Automated) ................................... 253 2.1.18 Ensure web server services are not in use (Automated) ............................................. 255 2.1.19 Ensure xinetd services are not in use (Automated) ..................................................... 258 2.1.20 Ensure X window server services are not in use (Automated) .................................... 261 2.1.21 Ensure mail transfer agents are configured for local-only mode (Automated) ............ 263 2.1.22 Ensure only approved services are listening on a network interface (Manual) ........... 266 2.2 Configure Client Services ........................................................................................................... 268 2.2.1 Ensure nis client is not installed (Automated) ................................................................ 269 Page 4 Internal Only - General 2.2.2 Ensure rsh client is not installed (Automated) ............................................................... 271 2.2.3 Ensure talk client is not installed (Automated) ............................................................... 273 2.2.4 Ensure telnet client is not installed (Automated) ........................................................... 275 2.2.5 Ensure ldap client is not installed (Automated) ............................................................. 277 2.2.6 Ensure ftp client is not installed (Automated) ................................................................ 279 2.3 Configure Time Synchronization ............................................................................................... 281 2.3.1 Ensure time synchronization is in use................................................................................. 282 2.3.1.1 Ensure a single time synchronization daemon is in use (Automated) ........................ 283 2.3.2 Configure systemd-timesyncd.............................................................................................. 287 2.3.2.1 Ensure systemd-timesyncd configured with authorized timeserver (Automated) ...... 289 2.3.2.2 Ensure systemd-timesyncd is enabled and running (Automated) .............................. 293 2.3.3 Configure chrony ................................................................................................................... 295 2.3.3.1 Ensure chrony is configured with authorized timeserver (Automated) ....................... 296 2.3.3.2 Ensure chrony is running as user _chrony (Automated) ............................................ 300 2.3.3.3 Ensure chrony is enabled and running (Automated) .................................................. 302 2.4 Job Schedulers ............................................................................................................................ 304 2.4.1 Configure cron ........................................................................................................................ 305 2.4.1.1 Ensure cron daemon is enabled and active (Automated) .......................................... 306 2.4.1.2 Ensure access to /etc/crontab is configured (Automated) .......................................... 308 2.4.1.3 Ensure access to /etc/cron.hourly is configured (Automated) .................................... 310 2.4.1.4 Ensure access to /etc/cron.daily is configured (Automated) ...................................... 312 2.4.1.5 Ensure access to /etc/cron.weekly is configured (Automated) ................................... 314 2.4.1.6 Ensure access to /etc/cron.monthly is configured (Automated) ................................. 316 2.4.1.7 Ensure access to /etc/cron.yearly is configured (Automated) .................................... 318 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated) ............................................ 319 2.4.1.9 Ensure access to crontab is configured (Automated) ................................................. 321 2.4.2 Configure at ............................................................................................................................ 325 2.4.2.1 Ensure access to at is configured (Automated) .......................................................... 326 3 Network ............................................................................................................................329 3.1 Configure Network Devices ........................................................................................................ 330 3.1.1 Ensure IPv6 status is identified (Manual) ...................................................................... 331 3.1.2 Ensure wireless interfaces are not available (Automated) ............................................ 333 3.1.3 Ensure bluetooth services are not in use (Automated).................................................. 336 3.2 Configure Network Kernel Modules ........................................................................................... 339 3.2.1 Ensure dccp kernel module is not available (Automated) ............................................. 340 3.2.2 Ensure tipc kernel module is not available (Automated) ............................................... 343 3.2.3 Ensure rds kernel module is not available (Automated) ................................................ 346 3.2.4 Ensure sctp kernel module is not available (Automated) .............................................. 349 3.3 Configure Network Kernel Parameters ...................................................................................... 352 3.3.1 Configure IPv4 parameters ................................................................................................... 353 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated) .............................................. 354 3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured (Automated) .................................. 358 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured (Automated) ........................... 363 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured (Automated) ........................... 368 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured (Automated) .................... 373 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is configured (Automated) ... 378 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is configured (Automated) .............. 382 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured (Automated) ........................ 386 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is configured (Automated) ................. 390 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured (Automated) ...................... 394 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is configured (Automated) ............... 398 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured (Automated) ..................................... 402 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured (Automated) .............................. 406 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is configured (Automated) ............... 410 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is configured (Automated) ........ 414 Page 5 Internal Only - General 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured (Automated) ............................ 418 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured (Automated) ..................... 422 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured (Automated) ..................................... 426 3.3.2 Configure IPv6 parameters ................................................................................................... 430 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured (Automated) .................................. 431 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured (Automated) ........................... 435 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured (Automated) ........................ 439 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is configured (Automated) ................. 443 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is configured (Automated) ................. 447 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is configured (Automated) .......... 451 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured (Automated) ................................... 455 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured (Automated) ............................ 459 4 Host Based Firewall .........................................................................................................463 4.1 Configure Uncomplicated Firewall ............................................................................................. 464 4.1.1 Ensure ufw is installed (Automated) .............................................................................. 465 4.1.2 Ensure ufw service is configured (Automated) .............................................................. 467 4.1.3 Ensure ufw incoming default is configured (Automated) ............................................... 470 4.1.4 Ensure ufw outgoing default is configured (Automated) ................................................ 472 4.1.5 Ensure ufw routed default is configured (Automated) ................................................... 474 5 Access Control ................................................................................................................475 5.1 Configure SSH Server ................................................................................................................. 476 5.1.1 Ensure access to /etc/ssh/sshd_config is configured (Automated) ............................... 478 5.1.2 Ensure access to SSH private host key files is configured (Automated)....................... 481 5.1.3 Ensure access to SSH public host key files is configured (Automated) ........................ 485 5.1.4 Ensure sshd access is configured (Automated) ............................................................ 489 5.1.5 Ensure sshd Banner is configured (Automated) ............................................................ 492 5.1.6 Ensure sshd Ciphers are configured (Automated) ........................................................ 494 5.1.7 Ensure sshd ClientAliveInterval and ClientAliveCountMax are configured (Automated) ................................................................................................................................................ 497 5.1.8 Ensure sshd DisableForwarding is enabled (Automated) ............................................. 500 5.1.9 Ensure sshd GSSAPIAuthentication is disabled (Automated) ...................................... 503 5.1.10 Ensure sshd HostbasedAuthentication is disabled (Automated) ................................. 505 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated) .................................................... 507 5.1.12 Ensure sshd KexAlgorithms is configured (Automated) .............................................. 509 5.1.13 Ensure sshd LoginGraceTime is configured (Automated) ........................................... 512 5.1.14 Ensure sshd LogLevel is configured (Automated) ....................................................... 514 5.1.15 Ensure sshd MACs are configured (Automated) ......................................................... 516 5.1.16 Ensure sshd MaxAuthTries is configured (Automated) ............................................... 519 5.1.17 Ensure sshd MaxSessions is configured (Automated) ................................................ 521 5.1.18 Ensure sshd MaxStartups is configured (Automated) ................................................. 523 5.1.19 Ensure sshd PermitEmptyPasswords is disabled (Automated) .................................. 525 5.1.20 Ensure sshd PermitRootLogin is disabled (Automated) .............................................. 527 5.1.21 Ensure sshd PermitUserEnvironment is disabled (Automated) .................................. 529 5.1.22 Ensure sshd UsePAM is enabled (Automated) ........................................................... 531 5.2 Configure privilege escalation ................................................................................................... 533 5.2.1 Ensure sudo is installed (Automated) ............................................................................ 534 5.2.2 Ensure sudo commands use pty (Automated) .............................................................. 536 5.2.3 Ensure sudo log file exists (Automated) ........................................................................ 538 5.2.4 Ensure users must provide password for escalation (Automated) ................................ 540 5.2.5 Ensure re-authentication for privilege escalation is not disabled globally (Automated) 542 5.2.6 Ensure sudo timestamp_timeout is configured (Automated) ......................................... 544 5.2.7 Ensure access to the su command is restricted (Automated) ....................................... 546 5.3 Pluggable Authentication Modules ............................................................................................ 548 5.3.1 Configure PAM software packages ...................................................................................... 549 5.3.1.1 Ensure latest version of pam is installed (Automated) ............................................... 550 Page 6 Internal Only - General 5.3.1.2 Ensure latest version of libpam-modules is installed (Automated) ............................. 552 5.3.1.3 Ensure latest version of libpam-pwquality is installed (Automated) ........................... 553 5.3.2 Configure pam-auth-update profiles .................................................................................... 555 5.3.2.1 Ensure pam_unix module is enabled (Automated)..................................................... 556 5.3.2.2 Ensure pam_faillock module is enabled (Automated) ................................................ 558 5.3.2.3 Ensure pam_pwquality module is enabled (Automated) ............................................ 561 5.3.2.4 Ensure pam_pwhistory module is enabled (Automated) ............................................ 564 5.3.3 Configure PAM Arguments ................................................................................................... 567 5.3.3.1 Configure pam_faillock module ...................................................................................... 568 5.3.3.1.1 Ensure password failed attempts lockout is configured (Automated)...................... 569 5.3.3.1.2 Ensure password unlock time is configured (Automated) ....................................... 571 5.3.3.1.3 Ensure password failed attempts lockout includes root account (Automated) ........ 573 5.3.3.2 Configure pam_pwquality module .................................................................................. 576 5.3.3.2.1 Ensure password number of changed characters is configured (Automated) ........ 578 5.3.3.2.2 Ensure minimum password length is configured (Automated) ................................ 581 5.3.3.2.3 Ensure password complexity is configured (Manual) .............................................. 584 5.3.3.2.4 Ensure password same consecutive characters is configured (Automated) ........... 588 5.3.3.2.5 Ensure password maximum sequential characters is configured (Automated) ...... 591 5.3.3.2.6 Ensure password dictionary check is enabled (Automated) .................................... 594 5.3.3.2.7 Ensure password quality checking is enforced (Automated) ................................... 597 5.3.3.2.8 Ensure password quality is enforced for the root user (Automated) ....................... 599 5.3.3.3 Configure pam_pwhistory module ................................................................................. 602 5.3.3.3.1 Ensure password history remember is configured (Automated) ............................. 603 5.3.3.3.2 Ensure password history is enforced for the root user (Automated) ....................... 605 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok (Automated) .................................... 607 5.3.3.4 Configure pam_unix module ........................................................................................... 609 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated) .......................................... 610 5.3.3.4.2 Ensure pam_unix does not include remember (Automated) ................................... 613 5.3.3.4.3 Ensure pam_unix includes a strong password hashing algorithm (Automated) ..... 615 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated) ............................................. 619 5.4 User Accounts and Environment ............................................................................................... 621 5.4.1 Configure shadow password suite parameters .................................................................. 622 5.4.1.1 Ensure password expiration is configured (Automated) ............................................. 623 5.4.1.2 Ensure minimum password days is configured (Manual) ........................................... 626 5.4.1.3 Ensure password expiration warning days is configured (Automated) ....................... 629 5.4.1.4 Ensure strong password hashing algorithm is configured (Automated) ..................... 631 5.4.1.5 Ensure inactive password lock is configured (Automated) ......................................... 633 5.4.1.6 Ensure all users last password change date is in the past (Automated) .................... 635 5.4.2 Configure root and system accounts and environment .................................................... 636 5.4.2.1 Ensure root is the only UID 0 account (Automated) ................................................... 637 5.4.2.2 Ensure root is the only GID 0 account (Automated) ................................................... 638 5.4.2.3 Ensure group root is the only GID 0 group (Automated) ............................................ 640 5.4.2.4 Ensure root account access is controlled (Automated) .............................................. 641 5.4.2.5 Ensure root path integrity (Automated) ....................................................................... 643 5.4.2.6 Ensure root user umask is configured (Automated) ................................................... 646 5.4.2.7 Ensure system accounts do not have a valid login shell (Automated) ....................... 649 5.4.2.8 Ensure accounts without a valid login shell are locked (Automated) ......................... 651 5.4.3 Configure user default environment .................................................................................... 653 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated) ............................................... 654 5.4.3.2 Ensure default user shell timeout is configured (Automated) ..................................... 656 5.4.3.3 Ensure default user umask is configured (Automated) .............................................. 660 6 Logging and Auditing ......................................................................................................664 6.1 System Logging ........................................................................................................................... 665 6.1.1 Configure journald ................................................................................................................. 666 6.1.1.1 Configure systemd-journald service .............................................................................. 667 Page 7 Internal Only - General 6.1.1.1.1 Ensure journald service is active (Automated) ........................................................ 668 6.1.1.1.2 Ensure journald log file access is configured (Manual) ........................................... 670 6.1.1.1.3 Ensure journald log file rotation is configured (Manual) .......................................... 673 6.1.1.1.4 Ensure journald ForwardToSyslog is disabled (Automated) ................................... 675 6.1.1.1.5 Ensure journald Storage is configured (Automated)................................................ 679 6.1.1.1.6 Ensure journald Compress is configured (Automated) ............................................ 683 6.1.1.2 Configure systemd-journal-remote................................................................................. 687 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated) ........................................ 688 6.1.1.2.2 Ensure systemd-journal-upload authentication is configured (Manual)................... 690 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active (Automated) ....................... 693 6.1.1.2.4 Ensure systemd-journal-remote service is not in use (Automated) ......................... 695 6.1.2 Configure rsyslog................................................................................................................... 697 6.1.2.1 Ensure rsyslog is installed (Automated) ..................................................................... 698 6.1.2.2 Ensure rsyslog service is enabled and active (Automated) ........................................ 700 6.1.2.3 Ensure journald is configured to send logs to rsyslog (Automated) ........................... 702 6.1.2.4 Ensure rsyslog log file creation mode is configured (Automated) .............................. 706 6.1.2.5 Ensure rsyslog logging is configured (Manual) ........................................................... 708 6.1.2.6 Ensure rsyslog is configured to send logs to a remote log host (Manual) .................. 710 6.1.2.7 Ensure rsyslog is not configured to receive logs from a remote client (Automated) .. 712 6.1.2.8 Ensure logrotate is configured (Manual) ..................................................................... 714 6.1.3 Configure Logfiles.................................................................................................................. 716 6.1.3.1 Ensure access to all logfiles has been configured (Automated) ................................. 717 6.2 System Auditing ........................................................................................................................... 722 6.2.1 Configure auditd Service ....................................................................................................... 724 6.2.1.1 Ensure auditd packages are installed (Automated) .................................................... 725 6.2.1.2 Ensure auditd service is enabled and active (Automated) ......................................... 727 6.2.1.3 Ensure auditing for processes that start prior to auditd is enabled (Automated) ....... 729 6.2.1.4 Ensure audit_backlog_limit is configured (Automated) .............................................. 731 6.2.2 Configure Data Retention ...................................................................................................... 733 6.2.2.1 Ensure audit log storage size is configured (Automated) ........................................... 734 6.2.2.2 Ensure audit logs are not automatically deleted (Automated) .................................... 736 6.2.2.3 Ensure system is disabled when audit logs are full (Automated) ............................... 737 6.2.2.4 Ensure system warns when audit logs are low on space (Automated) ...................... 740 6.2.3 Configure auditd Rules .......................................................................................................... 743 6.2.3.1 Ensure changes to system administration scope (sudoers) is collected (Automated)744 6.2.3.2 Ensure actions as another user are always logged (Automated) ............................... 746 6.2.3.3 Ensure events that modify the sudo log file are collected (Automated) ..................... 750 6.2.3.4 Ensure events that modify date and time information are collected (Automated) ...... 753 6.2.3.5 Ensure events that modify the system's network environment are collected (Automated) ............................................................................................................................ 757 6.2.3.6 Ensure use of privileged commands are collected (Automated) ................................ 761 6.2.3.7 Ensure unsuccessful file access attempts are collected (Automated) ....................... 765 6.2.3.8 Ensure events that modify user/group information are collected (Automated) .......... 769 6.2.3.9 Ensure discretionary access control permission modification events are collected (Automated) ............................................................................................................................ 773 6.2.3.10 Ensure successful file system mounts are collected (Automated) ........................... 778 6.2.3.11 Ensure session initiation information is collected (Automated) ................................ 782 6.2.3.12 Ensure login and logout events are collected (Automated) ...................................... 785 6.2.3.13 Ensure file deletion events by users are collected (Automated) .............................. 788 6.2.3.14 Ensure events that modify the system's Mandatory Access Controls are collected (Automated) ............................................................................................................................ 792 6.2.3.15 Ensure successful and unsuccessful attempts to use the chcon command are collected (Automated) ............................................................................................................. 795 6.2.3.16 Ensure successful and unsuccessful attempts to use the setfacl command are collected (Automated) ............................................................................................................. 799 Page 8 Internal Only - General 6.2.3.17 Ensure successful and unsuccessful attempts to use the chacl command are collected (Automated) ............................................................................................................. 803 6.2.3.18 Ensure successful and unsuccessful attempts to use the usermod command are collected (Automated) ............................................................................................................. 807 6.2.3.19 Ensure kernel module loading unloading and modification is collected (Automated) ................................................................................................................................................ 811 6.2.3.20 Ensure the audit configuration is immutable (Automated) ........................................ 816 6.2.3.21 Ensure the running and on disk configuration is the same (Manual) ....................... 818 6.2.4 Configure auditd File Access ................................................................................................ 820 6.2.4.1 Ensure audit log files mode is configured (Automated) .............................................. 821 6.2.4.2 Ensure audit log files owner is configured (Automated) ............................................. 824 6.2.4.3 Ensure audit log files group owner is configured (Automated) ................................... 826 6.2.4.4 Ensure the audit log file directory mode is configured (Automated) ........................... 828 6.2.4.5 Ensure audit configuration files mode is configured (Automated) .............................. 830 6.2.4.6 Ensure audit configuration files owner is configured (Automated) ............................. 832 6.2.4.7 Ensure audit configuration files group owner is configured (Automated) ................... 834 6.2.4.8 Ensure audit tools mode is configured (Automated)................................................... 836 6.2.4.9 Ensure audit tools owner is configured (Automated) .................................................. 838 6.2.4.10 Ensure audit tools group owner is configured (Automated) ..................................... 839 6.3 Configure Filesystem Integrity Checking .................................................................................. 841 6.3.1 Ensure AIDE is installed (Automated) ........................................................................... 842 6.3.2 Ensure filesystem integrity is regularly checked (Automated) ....................................... 844 6.3.3 Ensure cryptographic mechanisms are used to protect the integrity of audit tools (Automated) ............................................................................................................................ 847 7 System Maintenance .......................................................................................................851 7.1 Configure system file and directory access ............................................................................. 852 7.1.1 Ensure access to /etc/passwd is configured (Automated) ............................................. 853 7.1.2 Ensure access to /etc/passwd- is configured (Automated) ........................................... 855 7.1.3 Ensure access to /etc/group is configured (Automated) ................................................ 857 7.1.4 Ensure access to /etc/group- is configured (Automated)............................................... 859 7.1.5 Ensure access to /etc/shadow is configured (Automated) ............................................ 861 7.1.6 Ensure access to /etc/shadow- is configured (Automated) ........................................... 863 7.1.7 Ensure access to /etc/gshadow is configured (Automated) .......................................... 865 7.1.8 Ensure access to /etc/gshadow- is configured (Automated) ......................................... 867 7.1.9 Ensure access to /etc/shells is configured (Automated) ................................................ 869 7.1.10 Ensure access to /etc/security/opasswd is configured (Automated) ........................... 871 7.1.11 Ensure world writable files and directories are secured (Automated) ......................... 873 7.1.12 Ensure no files or directories without an owner and a group exist (Automated) ......... 877 7.1.13 Ensure SUID and SGID files are reviewed (Manual) ................................................... 880 7.2 Local User and Group Settings .................................................................................................. 883 7.2.1 Ensure accounts in /etc/passwd use shadowed passwords (Automated) .................... 884 7.2.2 Ensure /etc/shadow password fields are not empty (Automated) ................................. 886 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group (Automated) ................................. 888 7.2.4 Ensure shadow group is empty (Automated) ................................................................ 890 7.2.5 Ensure no duplicate UIDs exist (Automated) ................................................................. 892 7.2.6 Ensure no duplicate GIDs exist (Automated) ................................................................ 894 7.2.7 Ensure no duplicate user names exist (Automated) ...................................................... 896 7.2.8 Ensure no duplicate group names exist (Automated).................................................... 898 7.2.9 Ensure local interactive user home directories are configured (Automated) ................. 900 7.2.10 Ensure local interactive user dot files access is configured (Automated) ................... 905 Appendix: Summary Table ....................................................................................... 910 Appendix: CIS Controls v7 IG 1 Mapped Recommendations ................................ 926 Appendix: CIS Controls v7 IG 2 Mapped Recommendations ................................ 930 Page 9 Internal Only - General Appendix: CIS Controls v7 IG 3 Mapped Recommendations ................................ 938 Appendix: CIS Controls v7 Unmapped Recommendations ................................... 947 Appendix: CIS Controls v8 IG 1 Mapped Recommendations ................................ 948 Appendix: CIS Controls v8 IG 2 Mapped Recommendations ................................ 953 Appendix: CIS Controls v8 IG 3 Mapped Recommendations ................................ 961 Appendix: CIS Controls v8 Unmapped Recommendations ................................... 970 Appendix: Change History ....................................................................................... 971 Page 10 Internal Only - General Overview All CIS Benchmarks™ (Benchmarks) focus on technical configuration settings used to maintain and/or increase the security of the addressed technology, and they should be used in conjunction with other essential cyber hygiene tasks like: • Monitoring the base operating system and applications for vulnerabilities and quickly updating with the latest security patches. • End-point protection (Antivirus software, Endpoint Detection and Response (EDR), etc.). • Logging and monitoring user and system activity. In the end, the Benchmarks are designed to be a key component of a comprehensive cybersecurity program. Important Usage Information All Benchmarks are available free for non-commercial use from the CIS Website. They can be used to manually assess and remediate systems and applications. In lieu of manual assessment and remediation, there are several tools available to assist with assessment: • CIS Configuration Assessment Tool (CIS-CAT® Pro Assessor) • CIS Benchmarks™ Certified 3rd Party Tooling These tools make the hardening process much more scalable for large numbers of systems and applications. NOTE: Some tooling focuses only on the Benchmark Recommendations that can be fully automated (skipping ones marked Manual). It is important that ALL Recommendations (Automated and Manual) be addressed since all are important for properly securing systems and are typically in scope for audits. Key Stakeholders Cybersecurity is a collaborative effort, and cross functional cooperation is imperative within an organization to discuss, test, and deploy Benchmarks in an effective and efficient way. The Benchmarks are developed to be best practice configuration guidelines applicable to a wide range of use cases. In some organizations, exceptions to specific Recommendations will be needed, and this team should work to prioritize the problematic Recommendations based on several factors like risk, time, cost, and labor. These exceptions should be properly categorized and documented for auditing purposes. Page 11 Internal Only - General Apply the Correct Version of a Benchmark Benchmarks are developed and tested for a specific set of products and versions and applying an incorrect Benchmark to a system can cause the resulting pass/fail score to be incorrect. This is due to the assessment of settings that do not apply to the target systems. To assure the correct Benchmark is being assessed: • Deploy the Benchmark applicable to the way settings are managed in the environment: An example of this is the Microsoft Windows family of Benchmarks, which have separate Benchmarks for Group Policy, Intune, and Stand-alone systems based upon how system management is deployed. Applying the wrong Benchmark in this case will give invalid results. • Use the most recent version of a Benchmark: This is true for all Benchmarks, but especially true for cloud technologies. Cloud technologies change frequently and using an older version of a Benchmark may have invalid methods for auditing and remediation. Exceptions The guidance items in the Benchmarks are called recommendations and not requirements, and exceptions to some of them are expected and acceptable. The Benchmarks strive to be a secure baseline, or starting point, for a specific technology, with known issues identified during Benchmark development are documented in the Impact section of each Recommendation. In addition, organizational, system specific requirements, or local site policy may require changes as well, or an exception to a Recommendation or group of Recommendations (e.g. A Benchmark could Recommend that a Web server not be installed on the system, but if a system's primary purpose is to function as a Webserver, there should be a documented exception to this Recommendation for that specific server). In the end, exceptions to some Benchmark Recommendations are common and acceptable, and should be handled as follows: • The reasons for the exception should be reviewed cross-functionally and be well documented for audit purposes. • A plan should be developed for mitigating, or eliminating, the exception in the future, if applicable. • If the organization decides to accept the risk of this exception (not work toward mitigation or elimination), this should be documented for audit purposes. It is the responsibility of the organization to determine their overall security policy, and which settings are applicable to their unique needs based on the overall risk profile for the organization. Page 12 Internal Only - General Remediation CIS has developed Build Kits for many technologies to assist in the automation of hardening systems. Build Kits are designed to correspond to Benchmark's “Remediation” section, which provides the manual remediation steps necessary to make that Recommendation compliant to the Benchmark. When remediating systems (changing configuration settings on deployed systems as per the Benchmark's Recommendations), please approach this with caution and test thoroughly. The following is a reasonable remediation approach to follow: • CIS Build Kits, or internally developed remediation methods should never be applied to production systems without proper testing. • Proper testing consists of the following: o Understand the configuration (including installed applications) of the targeted systems. Various parts of the organization may need different configurations (e.g., software developers vs standard office workers). o Read the Impact section of the given Recommendation to help determine if there might be an issue with the targeted systems. o Test the configuration changes with representative lab system(s). If issues arise during testing, they can be resolved prior to deploying to any production systems. o When testing is complete, initially deploy to a small sub-set of production systems and monitor closely for issues. If there are issues, they can be resolved prior to deploying more broadly. o When the initial deployment above is completes successfully, iteratively deploy to additional systems and monitor closely for issues. Repeat this process until the full deployment is complete. Summary Using the Benchmarks Certified tools, working as a team with key stakeholders, being selective with exceptions, and being careful with remediation deployment, it is possible to harden large numbers of deployed systems in a cost effective, efficient, and safe manner. NOTE: As previously stated, the PDF versions of the CIS Benchmarks™ are available for free, non-commercial use on the CIS Website. All other formats of the CIS Benchmarks™ (MS Word, Excel, and Build Kits) are available for CIS SecureSuite® members. CIS-CAT® Pro is also available to CIS SecureSuite® members. Page 13 Internal Only - General Target Technology Details This document provides prescriptive guidance for establishing a secure configuration posture for Ubuntu Linux 22.04 LTS running on x86_64 platforms. This guide was developed and tested against Ubuntu 22.04.5 LTS The guidance within broadly assumes that operations are being performed as the root user, and executed under the default Bash version for the applicable distribution. Operations performed using sudo instead of the root user, or executed under another shell, may produce unexpected results, or fail to make the intended changes to the system. Non-root users may not be able to access certain areas of the system, especially after remediation has been performed. It is advisable to verify root users path integrity and the integrity of any programs being run prior to execution of commands and scripts included in this benchmark. The default prompt for the root user is #, and as such all sample commands will have # as an additional indication that it is to be executed as root. To obtain the latest version of this guide, please visit https://workbench.cisecurity.org. If you have questions, comments, or have identified ways to improve this guide, please write us at feedback@cisecurity.org. Intended Audience This benchmark is intended for system and application administrators, security specialists, auditors, help desk, and platform deployment personnel who plan to develop, deploy, assess, or secure solutions that incorporate Ubuntu Linux 22.04 LTS on x86_64 platforms. Page 14 Internal Only - General Consensus Guidance This CIS Benchmark™ was created using a consensus review process comprised of a global community of subject matter experts. The process combines real world experience with data-based information to create technology specific guidance to assist users to secure their environments. Consensus participants provide perspective from a diverse set of backgrounds including consulting, software development, audit and compliance, security research, operations, government, and legal. Each CIS Benchmark undergoes two phases of consensus review. The first phase occurs during initial Benchmark development. During this phase, subject matter experts convene to discuss, create, and test working drafts of the Benchmark. This discussion occurs until consensus has been reached on Benchmark recommendations. The second phase begins after the Benchmark has been published. During this phase, all feedback provided by the Internet community is reviewed by the consensus team for incorporation in the Benchmark. If you are interested in participating in the consensus process, please visit https://workbench.cisecurity.org/. Page 15 Internal Only - General Typographical Conventions The following typographical conventions are used throughout this guide: Convention Meaning Used for blocks of code, command, and Stylized Monospace font script examples. Text should be interpreted exactly as presented. Used for inline code, commands, UI/Menu Monospace font selections or examples. Text should be interpreted exactly as presented. Text set in angle brackets denote a variable requiring substitution for a real value. Used to reference other relevant settings, CIS Benchmarks and/or Benchmark Italic font Communities. Also, used to denote the title of a book, article, or other publication. Additional information or caveats things like Notes, Warnings, or Cautions (usually just Bold font the word itself and the rest of the text normal). Page 16 Internal Only - General Recommendation Definitions The following defines the various components included in a CIS recommendation as applicable. If any of the components are not applicable it will be noted, or the component will not be included in the recommendation. Title Concise description for the recommendation's intended configuration. Assessment Status An assessment status is included for every recommendation. The assessment status indicates whether the given recommendation can be automated or requires manual steps to implement. Both statuses are equally important and are determined and supported as defined below: Automated Represents recommendations for which assessment of a technical control can be fully automated and validated to a pass/fail state. Recommendations will include the necessary information to implement automation. Manual Represents recommendations for which assessment of a technical control cannot be fully automated and requires all or some manual steps to validate that the configured state is set as expected. The expected state can vary depending on the environment. Profile A collection of recommendations for securing a technology or a supporting platform. Most benchmarks include at least a Level 1 and Level 2 Profile. Level 2 extends Level 1 recommendations and is not a standalone profile. The Profile Definitions section in the benchmark provides the definitions as they pertain to the recommendations included for the technology. Description Detailed information pertaining to the setting with which the recommendation is concerned. In some cases, the description will include the recommended value. Rationale Statement Detailed reasoning for the recommendation to provide the user a clear and concise understanding on the importance of the recommendation. Page 17 Internal Only - General Impact Statement Any security, functionality, or operational consequences that can result from following the recommendation. Audit Procedure Systematic instructions for determining if the target system complies with the recommendation. Remediation Procedure Systematic instructions for applying recommendations to the target system to bring it into compliance according to the recommendation. Default Value Default value for the given setting in this recommendation, if known. If not known, either not configured or not defined will be applied. References Additional documentation relative to the recommendation. CIS Critical Security Controls® (CIS Controls®) The mapping between a recommendation and the CIS Controls is organized by CIS Controls version, Safeguard, and Implementation Group (IG). The Benchmark in its entirety addresses the CIS Controls safeguards of (v7) “5.1 - Establish Secure Configurations” and (v8) '4.1 - Establish and Maintain a Secure Configuration Process” so individual recommendations will not be mapped to these safeguards. Additional Information Supplementary information that does not correspond to any other field but may be useful to the user. Page 18 Internal Only - General Profile Definitions The following configuration profiles are defined by this Benchmark: • Level 1 - Server Items in this profile intend to: o be practical and prudent; o provide a clear security benefit; and o not inhibit the utility of the technology beyond acceptable means. This profile is intended for servers. • Level 2 - Server This profile extends the "Level 1 - Server" profile. Items in this profile exhibit one or more of the following characteristics: o are intended for environments or use cases where security is paramount. o acts as defense in depth measure. o may negatively inhibit the utility or performance of the technology. This profile is intended for servers. • Level 1 - Workstation Items in this profile intend to: o be practical and prudent; o provide a clear security benefit; and o not inhibit the utility of the technology beyond acceptable means. This profile is intended for workstations. • Level 2 - Workstation This profile extends the "Level 1 - Workstation" profile. Items in this profile exhibit one or more of the following characteristics: o are intended for environments or use cases where security is paramount. o acts as defense in depth measure. o may negatively inhibit the utility or performance of the technology. This profile is intended for workstations. Page 19 Internal Only - General Acknowledgements This Benchmark exemplifies the great things a community of users, vendors, and subject matter experts can accomplish through consensus collaboration. The CIS community thanks the entire consensus team with special recognition to the following individuals who contributed greatly to the creation of this guide: This benchmark is based upon previous Linux benchmarks published and would not be possible without the contributions provided over the history of all of these benchmarks. The CIS community thanks everyone who has contributed to the Linux benchmarks. Contributor Ron Colvin Dave Billing Dominic Pace Koen Laevens Mark Birch Thomas Sjögren James Trigg Matthew Burket Marcus Burghardt Graham Eames Robert McSulla Chad Streck Ryan Jaynes Cory Sherman Simon John Steve Cobrin Justin Brown Mike Cross Kleber Leal Laurent Mesure Editor Jonathan Lewis Christopherson Eric Pinnell Randie Bejar Gokhan Lus Trevor Wood Page 20 Internal Only - General Recommendations 1 Initial Setup Items in this section are advised for all systems but may be difficult or require extensive preparation after the initial setup of the system. 1.1 Filesystem The file system is generally a built-in layer used to handle the data management of the storage. Page 21 Internal Only - General 1.1.1 Configure Filesystem Kernel Modules Several uncommon filesystem types are supported under Linux. Removing support for unneeded filesystem types reduces the local attack surface of the system. If a filesystem type is not needed it should be disabled. Native Linux file systems are designed to ensure that built-in security controls function as expected. Non-native filesystems can lead to unexpected consequences to both the security and functionality of the system and should be used with caution. Many filesystems are created for niche use cases and are not maintained and supported as the operating systems are updated and patched. Users of non-native filesystems should ensure that there is attention and ongoing support for them, especially in light of frequent operating system changes. Standard network connectivity and Internet access to cloud storage may make the use of non-standard filesystem formats to directly attach heterogeneous devices much less attractive. Note: This should not be considered a comprehensive list of filesystems. You may wish to consider additions to those listed here for your environment. For the current available file system modules on the system see ls /usr/lib/modules/**/kernel/fs | sort -u. Start up scripts Kernel modules loaded directly via insmod will ignore what is configured in the relevant /etc/modprobe.d/*.conf files. If modules are still being loaded after a reboot whilst having the correctly configured blacklist and install command, check for insmod entries in start up scripts such as .bashrc. Return values Using /bin/false as the command in disabling a particular module serves two purposes; to convey the meaning of the entry to the user and cause a non-zero return value. The latter can be tested for in scripts. Please note that insmod will ignore what is configured in the relevant configuration files. The preferred way to load modules is with modprobe. Page 22 Internal Only - General 1.1.1.1 Ensure cramfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the cramfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the cramfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="cramfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the cramfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the cramfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 23 Internal Only - General 2. verify the cramfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the cramfs kernel module is not loaded: # lsmod | grep 'cramfs' Nothing should be returned. Run the following command to verify the cramfs kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+cramfs\b' Verify the output includes: blacklist cramfs -AND EITHER- install cramfs /bin/false -OR- install cramfs /bin/true Example output: blacklist cramfs install cramfs /bin/false Remediation: Unload and disable the cramfs kernel module. 1. Run the following commands to unload the cramfs kernel module: # modprobe -r cramfs 2>/dev/null # rmmod cramfs 2>/dev/null 2. Perform the following to disable the cramfs kernel module: Create a file ending in .conf with install cramfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install cramfs /bin/false" >> /etc/modprobe.d/60- cramfs.conf Create a file ending in .conf with blacklist cramfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist cramfs" >> /etc/modprobe.d/60-cramfs.conf Page 24 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53: CM-7 a 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040025 | RULE ID: SV-230498r1069314 | CAT III 5. STIG ID: OL08-00-040025 | RULE ID: SV-248833r958478 | CAT III 6. STIG ID: RHEL-09-231195 | RULE ID: SV-257880r1044951 | CAT III 7. STIG ID: ALMA-09-029940 | RULE ID: SV-269344r1050226 | CAT II 8. STIG ID: OL09-00-000045 | RULE ID: SV-271448r1091056 | CAT III CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 25 Internal Only - General 1.1.1.2 Ensure freevxfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The freevxfs filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the freevxfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the freevxfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="freevxfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the freevxfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the freevxfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 26 Internal Only - General 2. Verify the freevxfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the freevxfs kernel module is not loaded: # lsmod | grep 'freevxfs' Nothing should be returned. Run the following command to verify the freevxfs kernel module is not loadable: modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+freevxfs\b' Verify the output includes: blacklist freevxfs -AND- install freevxfs /bin/false -OR- install freevxfs /bin/true Example output: blacklist freevxfs install freevxfs /bin/false Remediation: Unload and disable the freevxfs kernel module. 1. Run the following commands to unload the freevxfs kernel module: # modprobe -r freevxfs 2>/dev/null # rmmod freevxfs 2>/dev/null 2. Perform the following to disable the freevxfs kernel module: Create a file ending in .conf with install freevxfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install freevxfs /bin/false" >> /etc/modprobe.d/60- freevxfs.conf Create a file ending in .conf with blacklist freevxfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist freevxfs" >> /etc/modprobe.d/60-freevxfs.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 27 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 28 Internal Only - General 1.1.1.3 Ensure hfs kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The hfs filesystem type is a hierarchical filesystem that allows you to mount Mac OS filesystems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the hfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the hfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="hfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the hfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the hfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 29 Internal Only - General 2. Verify the hfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the hfs kernel module is not loaded: # lsmod | grep 'hfs' Nothing should be returned. Run the following command to verify the hfs kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+hfs\b' Verify the output includes: blacklist hfs -AND- install hfs /bin/false -OR- install hfs /bin/true Example output: blacklist hfs install hfs /bin/false Remediation: Unload and disable the hfs kernel module. 1. Run the following commands to unload the hfs kernel module: modprobe -r hfs 2>/dev/null rmmod hfs 2>/dev/null 2. Perform the following to disable the hfs kernel module: Create a file ending in .conf with install hfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install hfs /bin/false" >> /etc/modprobe.d/60-hfs.conf Create a file ending in .conf with blacklist hfs in the /etc/modprobe.d/ directory. Example: printf '%s\n' "" "blacklist hfs" >> /etc/modprobe.d/60-hfs.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 30 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 31 Internal Only - General 1.1.1.4 Ensure hfsplus kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The hfsplus filesystem type is a hierarchical filesystem designed to replace hfs that allows you to mount Mac OS filesystems. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the hfsplus kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the hfsplus kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="hfsplus" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the hfsplus kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the hfsplus filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 32 Internal Only - General 2. Verify the hfsplus kernel module is not loaded and not loadable by performing the following: Run the following command to verify the hfsplus kernel module is not loaded: # lsmod | grep 'hfsplus' Nothing should be returned. Run the following command to verify the hfsplus kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+hfsplus\b' Verify the output includes: blacklist hfsplus -AND- install hfsplus /bin/false -OR- install hfsplus /bin/true Example output: blacklist hfsplus install hfsplus /bin/false Remediation: Unload and disable the hfsplus kernel module. 1. Run the following commands to unload the hfsplus kernel module: # modprobe -r hfsplus 2>/dev/null # rmmod hfsplus 2>/dev/null 2. Perform the following to disable the hfsplus kernel module: Create a file ending in .conf with install hfsplus /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install hfsplus /bin/false" >> /etc/modprobe.d/60- hfsplus.conf Create a file ending in .conf with blacklist hfsplus in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist hfsplus" >> /etc/modprobe.d/60-hfsplus.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 33 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 34 Internal Only - General 1.1.1.5 Ensure jffs2 kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The jffs2 (journaling flash filesystem 2) filesystem type is a log-structured filesystem used in flash memory devices. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Audit: Verify the jffs2 kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the jffs2 kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="jffs2" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the jffs2 kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the jffs2 filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 35 Internal Only - General 2. Verify the jffs2 kernel module is not loaded and not loadable by performing the following: Run the following command to verify the jffs2 kernel module is not loaded: lsmod | grep 'jffs2' Nothing should be returned. Run the following command to verify the jffs2 kernel module is not loadable: modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+jffs2\b' Verify the output includes: blacklist jffs2 -AND- install jffs2 /bin/false -OR- install jffs2 /bin/true Example output: blacklist jffs2 install jffs2 /bin/false Remediation: Unload and disable the jffs2 kernel module. 1. Run the following commands to unload the jffs2 kernel module: # modprobe -r jffs2 2>/dev/null # rmmod jffs2 2>/dev/null 2. Perform the following to disable the jffs2 kernel module: Create a file ending in .conf with install jffs2 /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install jffs2 /bin/false" >> /etc/modprobe.d/60- jffs2.conf Create a file ending in .conf with blacklist jffs2 in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist jffs2" >> /etc/modprobe.d/60-jffs2.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 36 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 37 Internal Only - General 1.1.1.6 Ensure overlay kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The Linux overlay kernel module, commonly referred to as Overlayfs, is a union mount filesystem. It allows the user to overlay one file system on top of another, and creates a single, unified view. Rationale: The overlay kernel module has known CVE's: CVE-2023-32629, CVE-2023-2640, and CVE-2023-0386. Disabling the overlay kernel module reduces the local attack surface by removing support for unnecessary filesystem types and mitigates potential risks associated with unauthorized execution of setuid files, enhancing the overall system security. Impact: WARNING: If Container applications such as Docker, Kubernetes, Podman, Linux Containers (LXC), etc. are in use proceed with caution and consider the impact on containerized workloads, as disabling the overlay may severely disrupt containerization. Audit: Verify the overlay kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the overlay kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="overlayfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the overlay kernel module is not available on the system and no further audit steps are required. Page 38 Internal Only - General Note: Some systems may include the overlay kernel module as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the overlay kernel module is not loaded and not loadable by performing the following: Run the following command to verify the overlay kernel module is not loaded: # lsmod | grep 'overlay' Nothing should be returned Run the following command to verify the overlay kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+overlay\b' Verify the output includes: blacklist overlay -AND- install overlay /bin/false -OR- install overlay /bin/true Example output: blacklist overlay install overlay /bin/false Remediation: Unload and disable the overlay kernel module. 1. Run the following commands to unload the overlay kernel module: # modprobe -r overlay 2>/dev/null # rmmod overlay 2>/dev/null 2. Perform the following to disable the overlay kernel module: Create a file ending in .conf with install overlay /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install overlay /bin/false" >> /etc/modprobe.d/60- overlay.conf Create a file ending in .conf with blacklist overlay in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist overlay" >> /etc/modprobe.d/60-overlay.conf Page 39 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. https://docs.kernel.org/filesystems/overlayfs.html 5. https://wiki.archlinux.org/title/Overlay_filesystem 6. https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=overlayfs CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 40 Internal Only - General 1.1.1.7 Ensure squashfs kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A squashfs image can be used without having to first decompress the image. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Impact: As Snap packages utilize squashfs as a compressed filesystem, disabling squashfs will cause Snap packages to fail. Snap application packages of software are self-contained and work across a range of Linux distributions. This is unlike traditional Linux package management approaches, like APT or RPM, which require specifically adapted packages per Linux distribution on an application update and delay therefore application deployment from developers to their software's end-user. Snaps themselves have no dependency on any external store ("App store"), can be obtained from any source and can be therefore used for upstream software deployment. Page 41 Internal Only - General Audit: Verify the squashfs kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the squashfs kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="squashfs" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the squashfs kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the squashfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the squashfs kernel module is not loaded and not loadable by performing the following: Run the following command to verify the squashfs kernel module is not loaded: # lsmod | grep 'squashfs' Nothing should be returned. Run the following command to verify the squashfs kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+squashfs\b' Verify the output includes: blacklist squashfs -AND- install squashfs /bin/false -OR- install squashfs /bin/true Example output: blacklist squashfs install squashfs /bin/false Page 42 Internal Only - General Remediation: Unload and disable the squashfs kernel module. 1. Run the following commands to unload the squashfs kernel module: # modprobe -r squashfs 2>/dev/null # rmmod squashfs 2>/dev/null 2. Perform the following to disable the squashfs kernel module: Create a file ending in .conf with install squashfs /bin/false in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "install squashfs /bin/false" >> /etc/modprobe.d/60- squashfs.conf Create a file ending in .conf with blacklist squashfs in the /etc/modprobe.d/ directory. Example: # printf '%s\n' "" "blacklist squashfs" >> /etc/modprobe.d/60-squashfs.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: ALMA-09-030160 | RULE ID: SV-269346r1050228 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 43 Internal Only - General 1.1.1.8 Ensure udf kernel module is not available (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The udf filesystem type is the universal disk format used to implement ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is necessary to support writing DVDs and newer optical disc formats. Rationale: Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. Impact: Microsoft Azure requires the usage of udf. udf should not be disabled on systems run on Microsoft Azure. Audit: Verify the udf kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the udf kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="udf" l_mod_type="fs" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the udf kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the udf filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 44 Internal Only - General 2. Verify the udf kernel module is not loaded and not loadable by performing the following: Run the following command to verify the udf kernel module is not loaded: # lsmod | grep 'udf' Nothing should be returned Run the following command to verify the udf kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+udf\b' Verify the output includes: blacklist udf -AND- install udf /bin/false -OR- install udf /bin/true Example output: blacklist udf install udf /bin/false Remediation: Unload and disable the udf kernel module. 1. Run the following commands to unload the udf kernel module: # modprobe -r udf 2>/dev/null # rmmod udf 2>/dev/null 2. Perform the following to disable the udf kernel module: Create a file ending in .conf with install udf /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install udf /bin/false" >> /etc/modprobe.d/60-udf.conf Create a file ending in .conf with blacklist udf in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist udf" >> /etc/modprobe.d/60-udf.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: ALMA-09-030380 | RULE ID: SV-269348r1050230 | CAT II Page 45 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 46 Internal Only - General 1.1.1.9 Ensure usb-storage kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: USB storage provides a means to transfer and store files ensuring persistence and availability of the files independent of network connection status. Its popularity and utility has led to USB-based malware being a simple and common means for network infiltration and a first step to establishing a persistent threat within a networked environment. Rationale: Restricting USB access on the system will decrease the physical attack surface for a device and diminish the possible vectors to introduce malware. Satisfies: SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163 Impact: Disabling the usb-storage module will disable any usage of USB storage devices. If requirements and local site policy allow the use of such devices, other solutions should be configured accordingly instead. One example of a commonly used solution is USBGuard. Page 47 Internal Only - General Audit: Verify the usb-storage kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the usb-storage kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="usb-storage" l_mod_type="drivers" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the usb-storage kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the usb-storage filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. Verify the usb-storage kernel module is not loaded and not loadable by performing the following: Run the following command to verify the usb-storage kernel module is not loaded: # lsmod | grep -P -- 'usb(_|-)storage' Nothing should be returned Run the following command to verify the usb-storage kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+usb_storage\b' Verify the output includes: blacklist usb_storage -AND- install usb_storage /bin/false -OR- install usb_storage /bin/true Example output: blacklist usb_storage install usb_storage /bin/false Page 48 Internal Only - General Remediation: Unload and disable the usb-storage kernel module. 1. Run the following commands to unload the usb-storage kernel module: # modprobe -r usb-storage 2>/dev/null # rmmod usb-storage 2>/dev/null 2. Perform the following to disable the usb-storage kernel module: Create a file ending in .conf with install usb_storage /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install usb_storage /bin/false" >> /etc/modprobe.d/60- usb-storage.conf Create a file ending in .conf with blacklist usb_storage in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist usb_storage" >> /etc/modprobe.d/60-usb- storage.conf References: 1. CCI-000778 | CCI-001958 | CCI-003959 2. NIST SP 800-53 :: IA-3 | NIST SP 800-53 :: CM-7 (9) (b) 3. NIST SP 800-53A :: IA-3.1 (ii) 4. STIG ID: RHEL-08-040080 | RULE ID: SV-230503r1069316 | CAT II 5. STIG ID: OL08-00-040080 | RULE ID: SV-248837r986386 | CAT II 6. STIG ID: RHEL-09-291010 | RULE ID: SV-258034r1051267 | CAT II 7. STIG ID: ALMA-09-031370 | RULE ID: SV-269357r1050240 | CAT II 8. STIG ID: OL09-00-000047 | RULE ID: SV-271450r1092466 | CAT II 9. STIG ID: OL09-00-002332 | RULE ID: SV-271702r1091818 | CAT II 10. STIG ID: UBTU-22-291010 | RULE ID: SV-260540r986276 | CAT II 11. STIG ID: UBTU-24-300039 | RULE ID: SV-270718r1067128 | CAT II 12. STIG ID: SLES-15-010480 | RULE ID: SV-234856r958820 | CAT II Additional Information: An alternative solution to disabling the usb-storage module may be found in USBGuard. Use of USBGuard and construction of USB device policies should be done in alignment with site policy. Page 49 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 10.3 Disable Autorun and Autoplay for Removable Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. 13.7 Manage USB Devices v7 If USB storage devices are required, enterprise software should be used that can configure systems to allow the use of specific devices. An inventory of such ● ● devices should be maintained. Page 50 Internal Only - General 1.1.1.10 Ensure unused filesystems kernel modules are not available (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Filesystem kernel modules are pieces of code that can be dynamically loaded into the Linux kernel to extend its filesystem capabilities, or so-called base kernel, of an operating system. Filesystem kernel modules are typically used to add support for new hardware (as device drivers), or for adding system calls. Rationale: While loadable filesystem kernel modules are a convenient method of modifying the running kernel, this can be abused by attackers on a compromised system to prevent detection of their processes or files, allowing them to maintain control over the system. Many rootkits make use of loadable filesystem kernel modules in this way. Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it. The following filesystem kernel modules have known CVE's and should be made unavailable if no dependencies exist: • ceph - CVE-2022-0670 • cifs - CVE-2022-29869 • exfat CVE-2022-29973 • ext CVE-2022-1184 • fat CVE-2022-22043 • fscache CVE-2022-3630 • fuse CVE-2023-0386 • gfs2 CVE-2023-3212 • nfs_common CVE-2023-6660 • nfsd CVE-2022-43945 • smbfs_common CVE-2022-2585 Impact: This list may be quite extensive and covering all edges cases is difficult. Therefore, it's crucial to carefully consider the implications and dependencies before making any changes to the filesystem kernel module configurations. Page 51 Internal Only - General Audit: Verify filesystem kernel modules that are not in use on the system are disabled. Review currently loaded kernel modules to ensure they are needed and conform to local site policy. Note: The "Audit script" included at the bottom of the "Audit Procedure" will perform the steps included below. 1. Run the following command to generate a list of filesystem types currently mounted on the system. # findmnt -Dkerno fstype | sort -u Review the output. These filesystem types should either be excluded from the audit or if no longer needed, unmounted and disabled. Example output: devtmpfs ext4 tmpfs vfat 2. Run the following script to generate a list of all file system kernel modules currently installed on the system: #!/usr/bin/env bash { l_search="$(readlink -e /usr/lib/modules/ || readlink -e /lib/modules/)" a_module=() while IFS= read -r -d $'\0' l_module_dir; do if [ ! "$(basename "$l_module_dir")" = "nls" ]; then while IFS= read -r -d $'\0' l_module_file; do l_mname="$(basename "$l_module_file" | cut -d'.' -f1)" if [ -f "$l_module_file" ] && ! grep -Psiq -- '\b'"$l_mname"'\b' \ <<< "${a_module[*]}"; then a_module+=("$l_mname") fi done < <(find -L "$l_module_dir" -mindepth 1 -maxdepth 1 -type f - print0) fi done < <(find "$l_search"/**/kernel/fs/ -mindepth 1 -maxdepth 1 -type d ! -empty -print0) printf '%s\n' "" "${a_module[@]}" } The output is a list of the kernel modules included in the /usr/lib/modules/{KERNEL_VERSION}/kernel/fs/ or /lib/modules/{KERNEL_VERSION}/kernel/fs/ directories. This list has been sorted to be unique values, ignore items in the nls directory, and added to an array called a_module. Page 52 Internal Only - General 3. Run the following command to generate a list of modules currently loaded into the kernel: # lsmod 4. compare the output from the list generated in step 2 to the list of loaded modules generated by the lsmod command in step 3. Any module appearing in both lists is currently loaded into the kernel. Review these to verify they are needed and approved by local site policy 5. Run the following command to generate a list of modules that are set to be Deny Listed: blacklist {MODULE_NAME}, and/or set be be not loadable: install {MODULE_NAME} /bin/false or install {MODULE_NAME} /bin/true: # modprobe --showconfig | grep -Pi -- '^\h*(blacklist|install)\h+' 6. Verify all modules in the output from the list generated in step 2 are both Deny Listed: blacklist {MODULE_NAME} and set to be not loadable: install {MODULE_NAME} /bin/false or install {MODULE_NAME} /bin/true. Audit Script: Page 53 Internal Only - General #!/usr/bin/env bash { a_check=() a_output=() a_module=() a_output2=() a_output3=() l_search="$(readlink -e /usr/lib/modules/ || readlink -e /lib/modules/)" IFS=$'\n' read -r -d '' -a a_mounted < <(findmnt -Dkerno fstype \ | sort -u && printf '\0' ) IFS=$'\n' read -r -d '' -a a_lsmod < <(lsmod | awk '{print $1}' && printf '\0' ) IFS=$'\n' read -r -d '' -a a_showconfig < <(modprobe --showconfig | \ grep -Pi -- '^\h*(blacklist|install)\h+' && printf '\0') while IFS= read -r -d $'\0' l_module_dir; do if [ ! "$(basename "$l_module_dir")" = "nls" ]; then while IFS= read -r -d $'\0' l_module_file; do l_mname="$(basename "$l_module_file" | cut -d'.' -f1)" if [ -f "$l_module_file" ] && ! grep -Psiq -- '\b'"$l_mname"'\b' <<< "${a_module[*]}"; then a_module+=("$l_mname") fi done < <(find -L "$l_module_dir" -mindepth 1 -maxdepth 1 -type f - print0) fi done < <(find "$l_search"/**/kernel/fs/ -mindepth 1 -maxdepth 1 -type d ! -empty -print0) for l_module in "${a_module[@]}"; do if grep -Psoiq -- '\b'"$l_module"'\b' <<< "${a_mounted[*]}"; then a_output+=(" - \"$l_module\"") elif grep -Psoiq -- '\b'"$l_module"'\b' <<< "${a_lsmod[*]}"; then a_output2+=(" - \"$l_module\"") elif ! grep -Psioq -- '\binstall\h+'"${l_module//-/_}"'\h+\H+\b' <<< "${a_showconfig[*]}" || \ ! grep -Psioq -- '\bblacklist\h+'"${l_module//-/_}"'\b' <<< "${a_showconfig[*]}"; then a_output3+=(" - \"$l_module\"") fi done [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output[@]}\" kernel modules currently mounted:" "${a_output[@]}" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output2[@]}\" kernel modules currently loaded:" "${a_output2[@]}" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" \ "- There are \"${#a_output3[@]}\" Kernel modules currently loadable:" "${a_output3[@]}" } WARNING: disabling or denylisting filesystem modules that are in use on the system may be FATAL. It is extremely important to thoroughly review this list. Page 54 Internal Only - General Remediation: - IF - the module is available in the running kernel: • Unload the filesystem kernel module from the kernel • Create a file ending in .conf with install filesystem kernel modules /bin/false in the /etc/modprobe.d/ directory • Create a file ending in .conf with deny list filesystem kernel modules in the /etc/modprobe.d/ directory WARNING: unloading, disabling or denylisting filesystem modules that are in use on the system may be FATAL. It is extremely important to thoroughly review the filesystems returned by the audit before following the remediation procedure. Example of unloading the gfs2kernel module: modprobe -r gfs2 2>/dev/null rmmod gfs2 2>/dev/null Example of fully disabling the gfs2 kernel module: printf '%s\n' "" "blacklist gfs2" "install gfs2 /bin/false" >> /etc/modprobe.d/gfs2.conf Note: • Disable a kernel module by modifying the command above for each unused filesystem kernel module • The example gfs2 must be updated with the appropriate module name for the command or example script bellow to run correctly. Below is an example script that can be modified to use on various filesystem kernel modules manual remediation process: Example Script Page 55 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=(); l_dl="" # Initialize arrays and clear variables l_mod_name="gfs2" # set module name l_mod_type="fs" # set module type l_mod_path="$(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)" f_module_fix() { l_dl="y" # Set to ignore duplicate checks a_showconfig=() # Create array with modprobe output while IFS= read -r l_showconfig; do a_showconfig+=("$l_showconfig") done < <(modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+'"${l_mod_name//-/_}"'\b') if lsmod | grep "$l_mod_name" &> /dev/null; then # Check if the module is currently loaded a_output2+=(" - unloading kernel module: \"$l_mod_name\"") modprobe -r "$l_mod_name" 2>/dev/null; rmmod "$l_mod_name" 2>/dev/null fi if ! grep -Pq -- '\binstall\h+'"${l_mod_name//- /_}"'\h+(\/usr)?\/bin\/(true|false)\b' <<< "${a_showconfig[*]}"; then a_output2+=(" - setting kernel module: \"$l_mod_name\" to \"$(readlink -f /bin/false)\"") printf '%s\n' "install $l_mod_name $(readlink -f /bin/false)" >> /etc/modprobe.d/"$l_mod_name".conf fi if ! grep -Pq -- '\bblacklist\h+'"${l_mod_name//-/_}"'\b' <<< "${a_showconfig[*]}"; then a_output2+=(" - denylisting kernel module: \"$l_mod_name\"") printf '%s\n' "blacklist $l_mod_name" >> /etc/modprobe.d/"$l_mod_name".conf fi } for l_mod_base_directory in $l_mod_path; do # Check if the module exists on the system if [ -d "$l_mod_base_directory/${l_mod_name/-/\/}" ] && [ -n "$(ls -A "$l_mod_base_directory/${l_mod_name/-/\/}")" ]; then a_output3+=(" - \"$l_mod_base_directory\"") [[ "$l_mod_name" =~ overlay ]] && l_mod_name="${l_mod_name::-2}" [ "$l_dl" != "y" ] && f_module_fix else echo -e " - kernel module: \"$l_mod_name\" doesn't exist in \"$l_mod_base_directory\"" fi done [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " -- INFO --" " - module: \"$l_mod_name\" exists in:" "${a_output3[@]}" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" || printf '%s\n' "" " - No changes needed" printf '%s\n' "" " - remediation of kernel module: \"$l_mod_name\" complete" "" } Page 56 Internal Only - General References: 1. https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=filesystem CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 57 Internal Only - General 1.1.1.11 Ensure firewire-core kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: The IEEE 1394 (FireWire) is a serial bus standard for high-speed real-time communication. Rationale: Disabling FireWire protects the system against exploitation of any flaws in its implementation. Audit: Verify the firewire-core kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the firewire-core kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="firewire" l_mod_type="drivers" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the firewire-core kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the firewire-core filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 58 Internal Only - General 2. Verify the firewire-core kernel module is not loaded and not loadable by performing the following: Run the following command to verify the firewire-core kernel module is not loaded: # lsmod | grep -P -- 'firewire(_|-)core' Nothing should be returned Run the following command to verify the firewire-core kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+firewire(_|- )core\b' Verify the output includes: blacklist firewire_core -AND- install firewire_core /bin/false -OR- install firewire_core /bin/true Example output: blacklist firewire_core install firewire_core /bin/false Remediation: Unload and disable the firewire-core kernel module. 1. Run the following commands to unload the firewire-core kernel module: # modprobe -r firewire-core 2>/dev/null # rmmod firewire-core 2>/dev/null 2. Perform the following to disable the firewire-core kernel module: Create a file ending in .conf with install firewire-core /bin/false in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "install firewire-core /bin/false" >> /etc/modprobe.d/60- firewire-core.conf Create a file ending in .conf with blacklist firewire-core in the /etc/modprobe.d/ directory Example: # printf '%s\n' "" "blacklist firewire-core" >> /etc/modprobe.d/60-firewire- core.conf Page 59 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040026 | RULE ID: SV-230499r1069315 | CAT III 5. STIG ID: OL08-00-040026 | RULE ID: SV-248834r958478 | CAT III 6. STIG ID: RHEL-09-213055 | RULE ID: SV-257806r1044859 | CAT II 7. STIG ID: OL09-00-000042 | RULE ID: SV-271445r1091047 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 60 Internal Only - General 1.1.2 Configure Filesystem Partitions Directories that are used for system-wide functions can be further protected by placing them on separate partitions. This provides protection for resource exhaustion and enables the use of mounting options that are applicable to the directory's intended use. Users' data can be stored on separate partitions and have stricter mount options. A user partition is a filesystem that has been established for use by the users and does not contain software for system operations. The recommendations in this section are easier to perform during initial system installation. If the system is already installed, it is recommended that a full backup be performed before repartitioning the system. Note: -IF- you are repartitioning a system that has already been installed (This may require the system to be in single-user mode): • Mount the new partition to a temporary mountpoint e.g. mount /dev/sda2 /mnt • Copy data from the original partition to the new partition. e.g. cp -a /var/tmp/* /mnt • Verify that all data is present on the new partition. e.g. ls -la /mnt • Unmount the new partition. e.g. umount /mnt • Remove the data from the original directory that was in the old partition. e.g. rm -Rf /var/tmp/* Otherwise it will still consume space in the old partition that will be masked when the new filesystem is mounted. • Mount the new partition to the desired mountpoint. e.g. mount /dev/sda2 /var/tmp • Update /etc/fstab with the new mountpoint. e.g. /dev/sda2 /var/tmp xfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Page 61 Internal Only - General 1.1.2.1 Configure /tmp The /tmp directory is a world-writable directory used to store data used by the system and user applications for a short period of time. This data should have no expectation of surviving a reboot, as this directory is intended to be emptied after each reboot. Page 62 Internal Only - General 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /tmp directory is a world-writable directory used for temporary storage by all users and some applications. Note: If an entry for /tmp exists in /etc/fstab it will take precedence over entries in a systemd unit file. There is an exception to this when a system is diskless and connected to iSCSI, entries in /etc/fstab may not take precedence over a systemd unit file. Rationale: Making /tmp its own file system allows an administrator to set additional mount options such as the noexec option on the mount, making /tmp useless for an attacker to install executable code. It would also prevent an attacker from establishing a hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link would be broken, and the attacker would have his own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. This can be accomplished by either mounting tmpfs to /tmp, or creating a separate partition for /tmp. Impact: By design files saved to /tmp should have no expectation of surviving a reboot of the system. tmpfs is ram based and all files stored to tmpfs will be lost when the system is rebooted. If files need to be persistent through a reboot, they should be saved to /var/tmp not /tmp. Since the /tmp directory is intended to be world-writable, there is a risk of resource exhaustion if it is not bound to tmpfs or a separate partition. Running out of /tmp space is a problem regardless of what kind of filesystem lies under it, but in a configuration where /tmp is not a separate file system it will essentially have the whole disk available, as the default installation only creates a single / partition. On the other hand, a RAM-based /tmp (as with tmpfs) will almost certainly be much smaller, which can lead to applications filling up the filesystem much more easily. Another alternative is to create a dedicated partition for /tmp from a separate volume or disk. One of the downsides of a disk-based dedicated partition is that it will be slower than tmpfs which is RAM-based. Page 63 Internal Only - General Audit: Run the following command and verify the output shows that /tmp is mounted. Particular requirements pertaining to mount options are covered in ensuing sections. # findmnt -kn /tmp Example output: /tmp tmpfs tmpfs rw,nosuid,nodev,noexec Ensure that systemd will mount the /tmp partition at boot time. # systemctl is-enabled tmp.mount Example output: generated Verify output is not masked or disabled. Note: By default, systemd will output generated if there is an entry in /etc/fstab for /tmp. This just means systemd will use the entry in /etc/fstab instead of its default unit file configuration for /tmp. Remediation: First ensure that systemd is correctly configured to ensure that /tmp will be mounted at boot time. # systemctl unmask tmp.mount For specific configuration requirements of the /tmp mount for your environment, modify /etc/fstab. Example of using tmpfs with specific mount options: tmpfs /tmp tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 0 Note: the size=2G is an example of setting a specific size for tmpfs. Example of using a volume or disk with specific mount options. The source location of the volume or disk will vary depending on your environment: /tmp defaults,nodev,nosuid,noexec 0 0 References: 1. https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems/ 2. https://www.freedesktop.org/software/systemd/man/systemd-fstab-generator.html 3. https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt 4. CCI-000366 5. NIST SP 800-53 :: CM-6 b 6. NIST SP 800-53A :: CM-6.1 (iv) 7. STIG ID: RHEL-08-010543 | RULE ID: SV-230295r1017106 | CAT II 8. STIG ID: RHEL-09-231015 | RULE ID: SV-257844r1044918 | CAT II 9. STIG ID: ALMA-09-025540 | RULE ID: SV-269305r1050187 | CAT II Page 64 Internal Only - General Additional Information: /tmp can be configured to use tmpfs. tmpfs puts everything into the kernel internal caches and grows and shrinks to accommodate the files it contains and is able to swap unneeded pages out to swap space. It has maximum size limits which can be adjusted on the fly via mount -o remount. Since tmpfs lives completely in the page cache and on swap, all tmpfs pages will be shown as "Shmem" in /proc/meminfo and "Shared" in free. Notice that these counters also include shared memory. The most reliable way to get the count is using df and du. tmpfs has three mount options for sizing: • size: The limit of allocated bytes for this tmpfs instance. The default is half of your physical RAM without swap. If you oversize your tmpfs instances the machine will deadlock since the OOM handler will not be able to free that memory. • nr_blocks: The same as size, but in blocks of PAGE_SIZE. • nr_inodes: The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, whichever is the lower. These parameters accept a suffix k, m or g and can be changed on remount. The size parameter also accepts a suffix % to limit this tmpfs instance to that percentage of your physical RAM. The default, when neither size nor nr_blocks is specified, is size=50%. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 65 Internal Only - General 1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /tmp filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /tmp. Audit: - IF - a separate partition exists for /tmp, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /tmp | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040123 | RULE ID: SV-230511r958804 | CAT II 4. STIG ID: RHEL-09-231125 | RULE ID: SV-257866r958804 | CAT II 5. STIG ID: ALMA-09-026860 | RULE ID: SV-269317r1050199 | CAT II Additional Information: See the fstab(5) manual page for more information. Page 66 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 67 Internal Only - General 1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /tmp. Audit: - IF - a separate partition exists for /tmp, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /tmp | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040124 | RULE ID: SV-230512r958804 | CAT II 4. STIG ID: RHEL-09-231135 | RULE ID: SV-257868r958804 | CAT II 5. STIG ID: ALMA-09-027080 | RULE ID: SV-269319r1050201 | CAT II Additional Information: See the fstab(5) manual page for more information. Page 68 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 69 Internal Only - General 1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot run executable binaries from /tmp. Impact: Setting the noexec option on /tmp may prevent installation and/or updating of some 3rd party software. Audit: - IF - a separate partition exists for /tmp, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /tmp | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /tmp. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /tmp partition. Example: /tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /tmp with the configured options: # mount -o remount /tmp Page 70 Internal Only - General References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040125 | RULE ID: SV-230513r958804 | CAT II 4. STIG ID: RHEL-09-231130 | RULE ID: SV-257867r958804 | CAT II 5. STIG ID: ALMA-09-026970 | RULE ID: SV-269318r1050200 | CAT II Additional Information: See the fstab(5) manual page for more information. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 71 Internal Only - General 1.1.2.2 Configure /dev/shm The /dev/shm directory is a world-writable directory that can function as shared memory that facilitates inter process communication (IPC) Page 72 Internal Only - General 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /dev/shm directory is a world-writable directory that can function as shared memory that facilitates inter process communication (IPC). Rationale: Making /dev/shm its own file system allows an administrator to set additional mount options such as the noexec option on the mount, making /dev/shm useless for an attacker to install executable code. It would also prevent an attacker from establishing a hard link to a system setuid program and wait for it to be updated. Once the program was updated, the hard link would be broken and the attacker would have his own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. This can be accomplished by mounting tmpfs to /dev/shm. Impact: Since the /dev/shm directory is intended to be world-writable, there is a risk of resource exhaustion if it is not bound to a separate partition. /dev/shm utilizing tmpfs can be resized using the size={size} parameter in the relevant entry in /etc/fstab. Audit: - IF - /dev/shm is to be used on the system, run the following command and verify the output shows that /dev/shm is mounted. Particular requirements pertaining to mount options are covered in ensuing sections. # findmnt -kn /dev/shm Example output: /dev/shm tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,seclabel Page 73 Internal Only - General Remediation: For specific configuration requirements of the /dev/shm mount for your environment, modify /etc/fstab. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime,size=2G 0 0 References: 1. https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems/ 2. https://www.freedesktop.org/software/systemd/man/systemd-fstab-generator.html 3. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 74 Internal Only - General 1.1.2.2.2 Ensure nodev option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /dev/shm filesystem is not intended to support devices, set this option to ensure that users cannot attempt to create special devices in /dev/shm partitions. Audit: - IF - a separate partition exists for /dev/shm, verify that the nodev option is set. # findmnt -kn /dev/shm | grep -v 'nodev' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /dev/shm partition. See the fstab(5) manual page for more information. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040120 | RULE ID: SV-230508r958804 | CAT II 4. STIG ID: RHEL-09-231110 | RULE ID: SV-257863r958804 | CAT II 5. STIG ID: ALMA-09-026530 | RULE ID: SV-269314r1050196 | CAT II Page 75 Internal Only - General Additional Information: Some distributions mount /dev/shm through other means and require /dev/shm to be added to /etc/fstab even though it is already being mounted on boot. Others may configure /dev/shm in other locations and may override /etc/fstab configuration. Consult the documentation appropriate for your distribution. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 76 Internal Only - General 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Setting this option on a file system prevents users from introducing privileged programs onto the system and allowing non-root users to execute them. Audit: - IF - a separate partition exists for /dev/shm, verify that the nosuid option is set. # findmnt -kn /dev/shm | grep -v 'nosuid' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /dev/shm partition. See the fstab(5) manual page for more information. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040121 | RULE ID: SV-230509r958804 | CAT II 4. STIG ID: RHEL-09-231120 | RULE ID: SV-257865r1044946 | CAT II 5. STIG ID: ALMA-09-026750 | RULE ID: SV-269316r1050198 | CAT II Page 77 Internal Only - General Additional Information: Some distributions mount /dev/shm through other means and require /dev/shm to be added to /etc/fstab even though it is already being mounted on boot. Others may configure /dev/shm in other locations and may override /etc/fstab configuration. Consult the documentation appropriate for your distribution. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 78 Internal Only - General 1.1.2.2.4 Ensure noexec option set on /dev/shm partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Setting this option on a file system prevents users from executing programs from shared memory. This deters users from introducing potentially malicious software on the system. Audit: - IF - a separate partition exists for /dev/shm, verify that the noexec option is set. # findmnt -kn /dev/shm | grep -v 'noexec' Nothing should be returned Remediation: - IF - a separate partition exists for /dev/shm. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /dev/shm partition. Example: tmpfs /dev/shm tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /dev/shm with the configured options: # mount -o remount /dev/shm Note: It is recommended to use tmpfs as the device/filesystem type as /dev/shm is used as shared memory space by applications. References: 1. CCI-001764 2. NIST SP 800-53 :: CM-7 (2) 3. STIG ID: RHEL-08-040122 | RULE ID: SV-230510r958804 | CAT II 4. STIG ID: RHEL-09-231115 | RULE ID: SV-257864r958804 | CAT II 5. STIG ID: ALMA-09-026640 | RULE ID: SV-269315r1050197 | CAT II Page 79 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 80 Internal Only - General 1.1.2.3 Configure /home Please note that home directories can be mounted anywhere and are not necessarily restricted to /home, nor restricted to a single location, nor is the name restricted in any way. Finding user home directories can be done by looking in /etc/passwd, looking over the mounted file systems with mount or querying the relevant database with getent. The following script can be run to find user's home directories: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed - rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3>='"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 != 65534) && $(NF) ~ pat) {print $1 " - " $6}' /etc/passwd } Page 81 Internal Only - General 1.1.2.3.1 Ensure separate partition exists for /home (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /home directory is used to support disk storage needs of local users. Rationale: The default installation only creates a single / partition. Since the /home directory contains user generated data, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. In addition, other operations on the system could fill up the disk unrelated to /home and impact all local users. Configuring /home as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. In the case of /home options such as usrquota/grpquota may be considered to limit the impact that users can have on each other with regards to disk resource exhaustion. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /home contains user data, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /home is mounted: # findmnt -kn /home /home /dev/sdb ext4 rw,nosuid,nodev,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /home. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. Page 82 Internal Only - General References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 Additional Information: When modifying /home it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 83 Internal Only - General 1.1.2.3.2 Ensure nodev option set on /home partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /home filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /home. Audit: - IF - a separate partition exists for /home, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /home | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /home. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /home partition. Example: /home defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /home with the configured options: # mount -o remount /home References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 84 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 85 Internal Only - General 1.1.2.3.3 Ensure nosuid option set on /home partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /home filesystem is only intended for user file storage, set this option to ensure that users cannot create setuid files in /home. Audit: - IF - a separate partition exists for /home, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /home | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /home. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /home partition. Example: /home defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /home with the configured options: # mount -o remount /home References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 86 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 87 Internal Only - General 1.1.2.4 Configure /var The /var directory is used by daemons and other system services to temporarily store dynamic data. Some directories created by these processes may be world-writable. Page 88 Internal Only - General 1.1.2.4.1 Ensure separate partition exists for /var (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var directory is used by daemons and other system services to temporarily store dynamic data. Some directories created by these processes may be world-writable. Rationale: The reasoning for mounting /var on a separate partition is as follows. The default installation only creates a single / partition. Since the /var directory may contain world writable files and directories, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system. In addition, other operations on the system could fill up the disk unrelated to /var and cause unintended behavior across the system as the disk is full. See man auditd.conf for details. Configuring /var as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. An example of exploiting /var may be an attacker establishing a hard-link to a system setuid program and waiting for it to be updated. Once the program is updated, the hard-link can be broken and the attacker would have their own copy of the program. If the program happened to have a security vulnerability, the attacker could continue to exploit the known flaw. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Page 89 Internal Only - General Audit: Run the following command and verify output shows /var is mounted. Example: # findmnt -kn /var /var /dev/sdb ext4 rw,nosuid,nodev,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 3. RHEL 8 STIG Vul ID: V-244529 4. RHEL 8 STIG Rule ID: SV-244529r902737 Additional Information: When modifying /var it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 90 Internal Only - General 1.1.2.4.2 Ensure nodev option set on /var partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var. Audit: - IF - a separate partition exists for /var, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var partition. Example: /var defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /var with the configured options: # mount -o remount /var References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 91 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 92 Internal Only - General 1.1.2.4.3 Ensure nosuid option set on /var partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var filesystem is only intended for variable files such as logs, set this option to ensure that users cannot create setuid files in /var. Audit: - IF - a separate partition exists for /var, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var partition. Example: /var defaults,rw,nosuid,nodev,relatime 0 0 Run the following command to remount /var with the configured options: # mount -o remount /var References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 93 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 94 Internal Only - General 1.1.2.5 Configure /var/tmp The /var/tmp directory is a world-writable directory used for temporary storage by all users and some applications. Temporary files residing in /var/tmp are to be preserved between reboots. Page 95 Internal Only - General 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var/tmp directory is a world-writable directory used for temporary storage by all users and some applications. Temporary files residing in /var/tmp are to be preserved between reboots. Rationale: The default installation only creates a single / partition. Since the /var/tmp directory is world-writable, there is a risk of resource exhaustion. In addition, other operations on the system could fill up the disk unrelated to /var/tmp and cause potential disruption to daemons as the disk is full. Configuring /var/tmp as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/tmp is mounted. Example: # findmnt -kn /var/tmp /var/tmp /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/tmp. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. Page 96 Internal Only - General References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-244529 5. RHEL 8 STIG Rule ID: SV-244529r902737 Additional Information: When modifying /var/tmp it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 97 Internal Only - General 1.1.2.5.2 Ensure nodev option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/tmp filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/tmp | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230520 5. RHEL 8 STIG Rule ID: SV-230520r854061 Page 98 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 99 Internal Only - General 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot create setuid files in /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/tmp | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230521 5. RHEL 8 STIG STIG ID: RHEL-08-040133 Page 100 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 101 Internal Only - General 1.1.2.5.4 Ensure noexec option set on /var/tmp partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/tmp filesystem is only intended for temporary file storage, set this option to ensure that users cannot run executable binaries from /var/tmp. Audit: - IF - a separate partition exists for /var/tmp, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/tmp | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/tmp. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/tmp partition. Example: /var/tmp defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/tmp with the configured options: # mount -o remount /var/tmp References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230522 5. RHEL 8 STIG Rule ID: SV-230522r854063 Page 102 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 103 Internal Only - General 1.1.2.6 Configure /var/log The /var/log directory is used by system services to store log data. Page 104 Internal Only - General 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The /var/log directory is used by system services to store log data. Rationale: The default installation only creates a single / partition. Since the /var/log directory contains log files which can grow quite large, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. Configuring /var/log as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attackers ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /var/log contains log files, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing, or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/log is mounted: # findmnt -kn /var/log /var/log /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/log . For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. Page 105 Internal Only - General References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5:: CM-6 b CM-7 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-230293 5. RHEL 8 STIG Rule ID: SV-230293r902720 Additional Information: When modifying /var/log it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multiuser mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 106 Internal Only - General 1.1.2.6.2 Ensure nodev option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/log filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/log | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230514 5. RHEL 8 STIG Rule ID: SV-230514r854055 Page 107 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 108 Internal Only - General 1.1.2.6.3 Ensure nosuid option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/log filesystem is only intended for log files, set this option to ensure that users cannot create setuid files in /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/log | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230515 5. RHEL 8 STIG Rule ID: SV-230515r854056 Page 109 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 110 Internal Only - General 1.1.2.6.4 Ensure noexec option set on /var/log partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/log filesystem is only intended for log files, set this option to ensure that users cannot run executable binaries from /var/log. Audit: - IF - a separate partition exists for /var/log, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/log | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/log. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/log partition. Example: /var/log defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log with the configured options: # mount -o remount /var/log References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. RHEL 8 STIG Vul ID: V-230516 5. RHEL 8 STIG Rule ID: SV-230516r854057 Page 111 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 112 Internal Only - General 1.1.2.7 Configure /var/log/audit The auditing daemon, auditd, stores log data in the /var/log/audit directory. Page 113 Internal Only - General 1.1.2.7.1 Ensure separate partition exists for /var/log/audit (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditing daemon, auditd, stores log data in the /var/log/audit directory. Rationale: The default installation only creates a single / partition. Since the /var/log/audit directory contains the audit.log file which can grow quite large, there is a risk of resource exhaustion. It will essentially have the whole disk available to fill up and impact the system as a whole. In addition, other operations on the system could fill up the disk unrelated to /var/log/audit and cause auditd to trigger its space_left_action as the disk is full. See man auditd.conf for details. Configuring /var/log/audit as its own file system allows an administrator to set additional mount options such as noexec/nosuid/nodev. These options limit an attacker's ability to create exploits on the system. Other options allow for specific behavior. See man mount for exact details regarding filesystem-independent and filesystem-specific options. As /var/log/audit contains audit logs, care should be taken to ensure the security and integrity of the data and mount point. Impact: Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations. Audit: Run the following command and verify output shows /var/log/audit is mounted: # findmnt -kn /var/log/audit /var/log/audit /dev/sdb ext4 rw,nosuid,nodev,noexec,relatime,seclabel Page 114 Internal Only - General Remediation: For new installations, during installation create a custom partition setup and specify a separate partition for /var/log/audit. For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate. References: 1. AJ Lewis, "LVM HOWTO", http://tldp.org/HOWTO/LVM-HOWTO/ 2. NIST SP 800-53 Rev. 5: CM-7 CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. RHEL 8 STIG Vul ID: V-230294 5. RHEL 8 STIG Rule ID: SV-230294r627750 Additional Information: When modifying /var/log/audit it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multi-user mode. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 115 Internal Only - General 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nodev mount option specifies that the filesystem cannot contain special devices. Rationale: Since the /var/log/audit filesystem is not intended to support devices, set this option to ensure that users cannot create a block or character special devices in /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the nodev option is set. Run the following command to verify that the nodev mount option is set. Example: # findmnt -kn /var/log/audit | grep -v nodev Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add nodev to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Revision 5 :: CM-7 (2) 3. STIG ID: RHEL-08-040129 | RULE ID: SV-230517r958804 | CAT II 4. STIG ID: RHEL-09-231175 | RULE ID: SV-257876r958804 | CAT II 5. STIG ID: ALMA-09-027190 | RULE ID: SV-269320r1050202 | CAT II Page 116 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 117 Internal Only - General 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nosuid mount option specifies that the filesystem cannot contain setuid files. Rationale: Since the /var/log/audit filesystem is only intended for variable files such as logs, set this option to ensure that users cannot create setuid files in /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the nosuid option is set. Run the following command to verify that the nosuid mount option is set. Example: # findmnt -kn /var/log/audit | grep -v nosuid Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add nosuid to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. STIG ID: RHEL-08-040130 | RULE ID: SV-230518r958804 | CAT II 5. STIG ID: RHEL-09-231170 | RULE ID: SV-257875r958804 | CAT II Page 118 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 119 Internal Only - General 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The noexec mount option specifies that the filesystem cannot contain executable binaries. Rationale: Since the /var/log/audit filesystem is only intended for audit logs, set this option to ensure that users cannot run executable binaries from /var/log/audit. Audit: - IF - a separate partition exists for /var/log/audit, verify that the noexec option is set. Run the following command to verify that the noexec mount option is set. Example: # findmnt -kn /var/log/audit | grep -v noexec Nothing should be returned Remediation: - IF - a separate partition exists for /var/log/audit. Edit the /etc/fstab file and add noexec to the fourth field (mounting options) for the /var/log/audit partition. Example: /var/log/audit defaults,rw,nosuid,nodev,noexec,relatime 0 0 Run the following command to remount /var/log/audit with the configured options: # mount -o remount /var/log/audit References: 1. See the fstab(5) manual page for more information. 2. NIST SP 800-53 Rev. 5: AC-3, MP-2 3. NIST SP 800-53 Revision 5 :: CM-7 (2) 4. STIG ID: RHEL-08-040131 | RULE ID: SV-230519r958804 | CAT II 5. STIG ID: RHEL-09-231165 | RULE ID: SV-257874r958804 | CAT II Page 120 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 121 Internal Only - General 1.2 Package Management Patch management procedures may vary widely between enterprises. Large enterprises may choose to install a local updates server that can be used in place of their distributions servers, whereas a single deployment of a system may prefer to get updates directly. Updates can be performed automatically or manually, depending on the site's policy for patch management. Organizations may prefer to test patches against their environment on a non-production system before rolling out to production. Outdated software is vulnerable to cyber criminals and hackers. Software updates help reduce the risk to your organization. The release of software update notes often reveals the patched exploitable entry points to the public. Public knowledge of these exploits can make your organization more vulnerable to malicious actors attempting to gain entry to your system's data. Software updates often offer new and improved features and speed enhancements. For the purpose of this benchmark, the requirement is to ensure that a patch management process is defined and maintained, the specifics of which are left to the organization. Page 122 Internal Only - General 1.2.1 Configure Package Repositories Patch management procedures may vary widely between enterprises. Large enterprises may choose to install a local updates server that can be used in place of their distributions servers, whereas a single deployment of a system may prefer to get updates directly. Updates can be performed automatically or manually, depending on the site's policy for patch management. Organizations may prefer to test patches against their environment on a non-production system before rolling out to production. Outdated software is vulnerable to cyber criminals and hackers. Software updates help reduce the risk to your organization. The release of software update notes often reveals the patched exploitable entry points to the public. Public knowledge of these exploits can leave your organization more vulnerable to malicious actors attempting to gain access to your system's data. Note: Creation of an appropriate patch management policy is left to the organization. Page 123 Internal Only - General 1.2.1.1 Ensure GPG keys are configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Most package managers implement GPG key signing to verify package integrity during installation. Rationale: It is important to ensure that updates are obtained from a valid source to protect against spoofing that could lead to the inadvertent installation of malware on the system. Page 124 Internal Only - General Audit: Verify GPG keys are configured correctly for your package manager: # apt-key list Note: • apt-key list is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)). • With the deprecation of apt-key it is recommended to use the Signed-By option in sources.list to require a repository to pass apt-secure(8) verification with a certain set of keys rather than all trusted keys apt has configured. - OR - 1. Run the following script and verify GPG keys are configured correctly for your package manager: #! /usr/bin/env bash { for file in /etc/apt/trusted.gpg.d/*.{gpg,asc} /etc/apt/sources.list.d/*.{gpg,asc} ; do if [ -f "$file" ]; then echo -e "File: $file" gpg --list-packets "$file" 2>/dev/null | awk '/keyid/ && !seen[$NF]++ {print "keyid:", $NF}' gpg --list-packets "$file" 2>/dev/null | awk '/Signed-By:/ {print "signed-by:", $NF}' echo -e fi done } 2. REVIEW and VERIFY to ensure that GPG keys are configured correctly for your package manager IAW site policy. Remediation: Update your package manager GPG keys in accordance with site policy. References: 1. NIST SP 800-53 Rev. 5: SI-2 2. https://manpages.debian.org/stretch/apt/sources.list.5.en.html Page 125 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 7.3 Perform Automated Operating System Patch v8 Management ● ● ● Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 7.4 Perform Automated Application Patch Management v8 Perform application updates on enterprise assets through automated patch ● ● ● management on a monthly, or more frequent, basis. 3.4 Deploy Automated Operating System Patch Management Tools v7 Deploy automated software update tools in order to ensure that the operating ● ● ● systems are running the most recent security updates provided by the software vendor. 3.5 Deploy Automated Software Patch Management Tools v7 Deploy automated software update tools in order to ensure that third-party ● ● ● software on all systems is running the most recent security updates provided by the software vendor. Page 126 Internal Only - General 1.2.1.2 Ensure package manager repositories are configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Systems need to have package manager repositories configured to ensure they receive the latest patches and updates. Rationale: If a system's package repositories are misconfigured important patches may not be identified or a rogue repository could introduce compromised software. Audit: Run the following command and verify package repositories are configured correctly: # apt-cache policy Remediation: Configure your package manager repositories according to site policy. References: 1. NIST SP 800-53 Rev. 5: SI-2 Page 127 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 7.3 Perform Automated Operating System Patch v8 Management ● ● ● Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 7.4 Perform Automated Application Patch Management v8 Perform application updates on enterprise assets through automated patch ● ● ● management on a monthly, or more frequent, basis. 3.4 Deploy Automated Operating System Patch Management Tools v7 Deploy automated software update tools in order to ensure that the operating ● ● ● systems are running the most recent security updates provided by the software vendor. 3.5 Deploy Automated Software Patch Management Tools v7 Deploy automated software update tools in order to ensure that third-party ● ● ● software on all systems is running the most recent security updates provided by the software vendor. Page 128 Internal Only - General 1.2.2 Configure Package Updates Page 129 Internal Only - General 1.2.2.1 Ensure updates, patches, and additional security software are installed (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Periodically patches are released for included software either due to security flaws or to include additional functionality. Rationale: Newer patches may contain security enhancements that would not be available through the latest full update. As a result, it is recommended that the latest software patches be used to take advantage of the latest functionality. As with any software installation, organizations need to determine if a given update meets their requirements and verify the compatibility and supportability of any additional software against the update revision that is selected. Audit: Verify there are no updates or patches to install: # apt update # apt -s upgrade Remediation: Run the following commands to update all packages following local site policy guidance on applying updates and patches: Run the following command to update the system with the available patches and updates: # apt update Run one of the following commands to apply the updates and patches: # apt upgrade - OR - # apt dist-upgrade Note: When running the command apt dist-upgrade that apt has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist-upgrade command may remove some packages. References: 1. NIST SP 800-53 Rev. 5: SI-2 Page 130 Internal Only - General Additional Information: Site policy may mandate a testing period before installation onto production systems for available updates. • upgrade - is used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list. Packages currently installed with new versions available are retrieved and upgraded; under no circumstances are currently installed packages removed, or packages not already installed retrieved and installed. New versions of currently installed packages that cannot be upgraded without changing the install status of another package will be left at their current version. An update must be performed first so that apt knows that new versions of packages are available. • dist-upgrade - in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary. So, dist- upgrade command may remove some packages. The /etc/apt/sources.list file contains a list of locations from which to retrieve desired package files. See also apt_preferences(5) for a mechanism for overriding the general settings for individual packages. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 7.3 Perform Automated Operating System Patch v8 Management ● ● ● Perform operating system updates on enterprise assets through automated patch management on a monthly, or more frequent, basis. 7.4 Perform Automated Application Patch Management v8 Perform application updates on enterprise assets through automated patch ● ● ● management on a monthly, or more frequent, basis. 3.4 Deploy Automated Operating System Patch Management Tools v7 Deploy automated software update tools in order to ensure that the operating ● ● ● systems are running the most recent security updates provided by the software vendor. 3.5 Deploy Automated Software Patch Management Tools v7 Deploy automated software update tools in order to ensure that third-party ● ● ● software on all systems is running the most recent security updates provided by the software vendor. Page 131 Internal Only - General 1.3 Mandatory Access Control Mandatory Access Control (MAC) provides an additional layer of access restrictions to processes on top of the base Discretionary Access Controls. By restricting how processes can access files and resources on a system the potential impact from vulnerabilities in the processes can be reduced. Impact: Mandatory Access Control limits the capabilities of applications and daemons on a system, while this can prevent unauthorized access the configuration of MAC can be complex and difficult to implement correctly preventing legitimate access from occurring. Page 132 Internal Only - General 1.3.1 Configure AppArmor AppArmor provides a Mandatory Access Control (MAC) system that greatly augments the default Discretionary Access Control (DAC) model. Under AppArmor MAC rules are applied by file paths instead of by security contexts as in other MAC systems. As such it does not require support in the filesystem and can be applied to network mounted filesystems for example. AppArmor security policies define what system resources applications can access and what privileges they can do so with. This automatically limits the damage that the software can do to files accessible by the calling user. The user does not need to take any action to gain this benefit. For an action to occur, both the traditional DAC permissions must be satisfied as well as the AppArmor MAC rules. The action will not be allowed if either one of these models does not permit the action. In this way, AppArmor rules can only make a system's permissions more restrictive and secure. References: 1. AppArmor Documentation: http://wiki.apparmor.net/index.php/Documentation 2. Ubuntu AppArmor Documentation: https://help.ubuntu.com/community/AppArmor 3. SUSE AppArmor Documentation: https://www.suse.com/documentation/apparmor/ Page 133 Internal Only - General 1.3.1.1 Ensure the apparmor packages are installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AppArmor provides Mandatory Access Controls. Rationale: Without a Mandatory Access Control system installed only the default Discretionary Access Control system will be available. Audit: Run the following command to verify that apparmor is installed: # dpkg-query -s apparmor &>/dev/null && echo "apparmor is installed" apparmor is installed Run the following command to verify that apparmor-utils is installed: # dpkg-query -s apparmor-utils &>/dev/null && echo "apparmor-utils is installed" apparmor-utils is installed Remediation: Run the following command to install apparmor and apparmor-utils: # apt install apparmor apparmor-utils References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 134 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 135 Internal Only - General 1.3.1.2 Ensure AppArmor is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AppArmor is a kernel enhancement to confine programs to a limited set of resources. AppArmor is enabled by default. Note: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Rationale: AppArmor is a security mechanism and disabling it is not recommended. Audit: Run the following command to verify that AppArmor has not been disabled: # grep "^\s*linux" /boot/grub/grub.cfg | grep "apparmor=0" Nothing should be returned. Remediation: Edit /etc/default/grub of file in /etc/default/grub.d and remove the apparmor=0 parameters to the GRUB_CMDLINE_LINUX= line Run the following commands to update the grub2 configuration and reboot the system: # update-grub # reboot References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 136 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 137 Internal Only - General 1.3.1.3 Ensure all AppArmor Profiles are not disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AppArmor profiles define what resources applications are able to access. Rationale: Security configuration requirements vary from site to site. Some sites may mandate a policy that is stricter than the default policy, which is perfectly acceptable. This item is intended to ensure that any policies that exist on the system are activated. Audit: Run the following command and verify that profiles are loaded, and are in either enforce or complain mode: # apparmor_status | grep profiles Review output and ensure that profiles are loaded, and in either enforce or complain mode: 37 profiles are loaded. 35 profiles are in enforce mode. 2 profiles are in complain mode. 4 processes have profiles defined. Run the following command and verify no processes are unconfined # apparmor_status | grep processes Review the output and ensure no processes are unconfined: 4 processes have profiles defined. 4 processes are in enforce mode. 0 processes are in complain mode. 0 processes are unconfined but have a profile defined. Remediation: Run the following command to set all profiles to enforce mode: # aa-enforce /etc/apparmor.d/* - OR - Run the following command to set all profiles to complain mode: # aa-complain /etc/apparmor.d/* Note: Any unconfined processes may need to have a profile created or activated for them and then be restarted Page 138 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AC-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 139 Internal Only - General 1.3.1.4 Ensure all AppArmor Profiles are enforcing (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: AppArmor profiles define what resources applications are able to access. Rationale: Security configuration requirements vary from site to site. Some sites may mandate a policy that is stricter than the default policy, which is perfectly acceptable. This item is intended to ensure that any policies that exist on the system are activated. Audit: Run the following commands and verify that profiles are loaded and are not in complain mode: # apparmor_status | grep profiles Review output and ensure that profiles are loaded, and in enforce mode: 34 profiles are loaded. 34 profiles are in enforce mode. 0 profiles are in complain mode. 2 processes have profiles defined. Run the following command and verify that no processes are unconfined: apparmor_status | grep processes Review the output and ensure no processes are unconfined: 2 processes have profiles defined. 2 processes are in enforce mode. 0 processes are in complain mode. 0 processes are unconfined but have a profile defined. Remediation: Run the following command to set all profiles to enforce mode: # aa-enforce /etc/apparmor.d/* Note: Any unconfined processes may need to have a profile created or activated for them and then be restarted References: 1. NIST SP 800-53 Rev. 5: AC-3 Page 140 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 141 Internal Only - General 1.4 Configure Bootloader The recommendations in this section focus on securing the bootloader and settings involved in the boot process directly. Page 142 Internal Only - General 1.4.1 Ensure bootloader password is set (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Setting the boot loader password will require that anyone rebooting the system must enter a password before being able to set command line boot parameters Rationale: Requiring a boot password upon execution of the boot loader will prevent an unauthorized user from entering boot parameters or changing the boot partition. This prevents users from weakening security (e.g. turning off AppArmor at boot time). Impact: If password protection is enabled, only the designated superuser can edit a GRUB 2 menu item by pressing "e" or access the GRUB 2 command line by pressing "c" If GRUB 2 is set up to boot automatically to a password-protected menu entry the user has no option to back out of the password prompt to select another menu entry. Holding the SHIFT key will not display the menu in this case. The user must enter the correct username and password. If unable to do so, the configuration files will have to be edited via a LiveCD or other means to fix the problem You can add --unrestricted to the menu entries to allow the system to boot without entering a password. A password will still be required to edit menu items. More Information: https://help.ubuntu.com/community/Grub2/Passwords Audit: Run the following commands and verify output matches: # grep "^set superusers" /boot/grub/grub.cfg set superusers="" # awk -F. '/^\s*password/ {print $1"."$2"."$3}' /boot/grub/grub.cfg password_pbkdf2 grub.pbkdf2.sha512 Page 143 Internal Only - General Remediation: Create an encrypted password with grub-mkpasswd-pbkdf2: # grub-mkpasswd-pbkdf2 --iteration-count=600000 --salt=64 Enter password: Reenter password: PBKDF2 hash of your password is Add the following into a custom /etc/grub.d configuration file: set superusers="" password_pbkdf2 The superuser/user information and password should not be contained in the /etc/grub.d/00_header file as this file could be overwritten in a package update. If there is a requirement to be able to boot/reboot without entering the password, edit /etc/grub.d/10_linux and add --unrestricted to the line CLASS= Example: CLASS="--class gnu-linux --class gnu --class os --unrestricted" Run the following command to update the grub2 configuration: # update-grub Default Value: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Replace /boot/grub/grub.cfg with the appropriate grub configuration file for your environment. References: 1. NIST SP 800-53 Rev. 5: AC-3 2. NIST SP 800-53A :: AC-3.1 Additional Information: Changes to /etc/grub.d/10_linux may be overwritten during updates to the grub- common package. You should review any changes to this file before rebooting otherwise the system may unexpectedly prompt for a password on the next boot. Page 144 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 145 Internal Only - General 1.4.2 Ensure access to bootloader config is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The grub configuration file contains information on boot settings and passwords for unlocking boot options. Rationale: Setting the permissions to read and write for root only prevents non-root users from seeing the boot parameters or changing them. Non-root users who read the boot parameters may be able to identify weaknesses in security upon boot and be able to exploit them. Audit: Run the following command and verify Uid and Gid are both 0/root and Access is 0600 or more restrictive. # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /boot/grub/grub.cfg Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set permissions on your grub configuration: # chown root:root /boot/grub/grub.cfg # chmod u-x,go-rwx /boot/grub/grub.cfg Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3 Additional Information: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment enact equivalent settings. Replace /boot/grub/grub.cfg with the appropriate grub configuration file for your environment Page 146 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 147 Internal Only - General 1.5 Configure Additional Process Hardening Page 148 Internal Only - General 1.5.1 Ensure randomize_va_space is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Address space layout randomization (ASLR) is an exploit mitigation technique which randomly arranges the address space of key data areas of a process. Rationale: Randomly placing virtual memory regions will make it difficult to write memory page exploits as the memory placement will be consistently shifting. Page 149 Internal Only - General Audit: Verify kernel.randomize_va_space is set to 2. 1. Run the following command to verify kernel.randomize_va_space is set to 2 in the running configuration: # sysctl kernel.randomize_va_space Verify output is: kernel.randomize_va_space = 2` 2. Run the following script to verify kernel.randomize_va_space is set to 2 in a sysctl conf file being used by systemd sysctl: #!/usr/bin/env bash { l_parameter_name="kernel.randomize_va_space" l_grep="${l_parameter_name//./\\.}" a_output=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufwscf="$([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_ufwscf" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - UFW set: \"$l_parameter_name\" to: \"$l_option_value\" in: \"$l_file\"") while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - \"$l_parameter_name\" is set to: \"$l_option_value\" in: \"$l_file\"") done < <("$l_systemdsysctl" --cat-config | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "kernel.randomize_va_space" is set to: "2" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Page 150 Internal Only - General Note: • If the UFW set value is displayed, and is the correct value, this is considered a passing state. If this value is incorrect, it must be updated in the file shown in the audit script output. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl do to system configuration changes. Page 151 Internal Only - General Remediation: 1. Review all files ending in .conf in the /etc/sysctl.d directory and comment out or remove all kernel.randomize_va_space lines that are not kernel.randomize_va_spacee=2. Example script: #!/usr/bin/env bash { l_option="kernel.randomize_va_space" l_grep="${l_option//./\\.}" l_value="2" while IFS= read -r -d $'\0' l_file; do grep -Poi '\h*'"$l_option"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*kernel.yama.ptrace_scope\s*=/s/^/# /' "$l_file" done < <(find /etc/sysctl.d/ -type f -name '*.conf' -print0) } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: kernel.randomize_va_space = 2 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.randomize_va_space = 2" >> /etc/sysctl.d/60- kernel_sysctl.conf 3. Run the following command to load all system configuration filles: # sysctl --system Default Value: kernel.randomize_va_space = 2 References: 1. CCI-002824 2. NIST SP 800-53 :: SI-16 3. STIG ID: RHEL-08-010430 | RULE ID: SV-230280r1017093 | CAT II 4. STIG ID: RHEL-09-213070 | RULE ID: SV-257809r1044866 | CAT II 5. STIG ID: ALMA-09-044900 | RULE ID: SV-269452r1050335 | CAT II 6. STIG ID: UBTU-22-213020 | RULE ID: SV-260474r958928 | CAT II 7. STIG ID: UBTU-24-700310 | RULE ID: SV-270772r1066805 | CAT II 8. STIG ID: SLES-15-010550 | RULE ID: SV-234862r958928 | CAT II Page 152 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.5 Enable Anti-Exploitation Features Enable anti-exploitation features on enterprise assets and software, where v8 possible, such as Microsoft® Data Execution Prevention (DEP), Windows® ● ● Defender Exploit Guard (WDEG), or Apple® System Integrity Protection (SIP) and Gatekeeper™. 8.3 Enable Operating System Anti-Exploitation Features/ Deploy Anti-Exploit Technologies v7 Enable anti-exploitation features such as Data Execution Prevention (DEP) or Address Space Layout Randomization (ASLR) that are available in an operating ● ● system or deploy appropriate toolkits that can be configured to apply protection to a broader set of applications and executables. Page 153 Internal Only - General 1.5.2 Ensure ptrace_scope is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The ptrace() system call provides a means by which one process (the "tracer") may observe and control the execution of another process (the "tracee"), and examine and change the tracee's memory and registers. The sysctl settings (writable only with CAP_SYS_PTRACE) are: • 0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other process running under the same uid, as long as it is dumpable (i.e. did not transition uids, start privileged, or have called prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is unchanged. • 1 - restricted ptrace: a process must have a predefined relationship with the inferior it wants to call PTRACE_ATTACH on. By default, this relationship is that of only its descendants when the above classic criteria is also met. To change the relationship, an inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare an allowed debugger PID to call PTRACE_ATTACH on the inferior. Using PTRACE_TRACEME is unchanged. • 2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace with PTRACE_ATTACH, or through children calling PTRACE_TRACEME. • 3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via PTRACE_TRACEME. Once set, this sysctl value cannot be changed. Rationale: If one application is compromised, it would be possible for an attacker to attach to other running processes (e.g. Bash, Firefox, SSH sessions, GPG agent, etc) to extract additional credentials and continue to expand the scope of their attack. Enabling restricted mode will limit the ability of a compromised process to PTRACE_ATTACH on other processes running under the same user. With restricted mode, ptrace will continue to work with root user. Page 154 Internal Only - General Audit: Verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3. 1. Run the following command to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in the running configuration: # sysctl kernel.yama.ptrace_scope Example output: kernel.yama.ptrace_scope = 1 2. Run the following script to verify kernel.yama.ptrace_scope is set to a value of: 1, 2, or 3 in a sysctl conf file being used by systemd sysctl: #!/usr/bin/env bash { l_parameter_name="kernel.yama.ptrace_scope" l_grep="${l_parameter_name//./\\.}" a_output=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufwscf="$([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_ufwscf" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - UFW set: \"$l_parameter_name\" to: \"$l_option_value\" in: \"$l_file\"") while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - \"$l_parameter_name\" is set to: \"$l_option_value\" in: \"$l_file\"") done < <("$l_systemdsysctl" --cat-config | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "kernel.yama.ptrace_scope" is set to: "1" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Page 155 Internal Only - General Note: • If the UFW set value is displayed, and is the correct value, this is considered a passing state. If this value is incorrect, it must be updated in the file shown in the audit script output. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl do to system configuration changes. Page 156 Internal Only - General Remediation: 1. Review all files ending in .conf in the /etc/sysctl.d directory and comment out or remove all kernel.yama.ptrace_scope lines that are not kernel.yama.ptrace_scope=1, kernel.yama.ptrace_scope=2, or kernel.yama.ptrace_scope=3. Example script: #!/usr/bin/env bash { l_option="kernel.yama.ptrace_scope" l_grep="${l_option//./\\.}" l_value="(1|2|3)" while IFS= read -r -d $'\0' l_file; do grep -Poi '\h*'"$l_option"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*kernel.yama.ptrace_scope\s*=/s/^/# /' "$l_file" done < <(find /etc/sysctl.d/ -type f -name '*.conf' -print0) } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: kernel.yama.ptrace_scope = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "kernel.yama.ptrace_scope = 1" >> /etc/sysctl.d/60- kernel_sysctl.conf Note: The example uses kernel.yama.ptrace_scope = 1 but value may be set to 1, 2, or 3 3. Run the following command to load all system configuration filles: # sysctl --system Default Value: kernel.yama.ptrace_scope = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040282 | RULE ID: SV-230546r1017308 | CAT II 5. STIG ID: RHEL-09-213080 | RULE ID: SV-257811r1044872 | CAT II 6. STIG ID: ALMA-09-040940 | RULE ID: SV-269424r1050307 | CAT II Page 157 Internal Only - General Additional Information: Ptrace is very rarely used by regular applications and is mostly used by debuggers such as gdb and strace. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 158 Internal Only - General 1.5.3 Ensure suid_dumpable is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: fs.suid_dumpable governs whether a privileged process (with the setuid bit) can generate a core dump, regardless of other configurations. fs.suid_dumpable values: • 0 (default) - Any process that has changed privilege levels (like SUID programs) or is execute-only will not dump core. • 1 (debug) - All processes dump core if possible. The core dump is owned by the current user and security is not applied. This is primarily intended for system debugging. • 2 (suidsafe) - Any binary that normally wouldn't be dumped is dumped, but only if the core_pattern is set to a pipe handler or a fully qualified path. This mode is suitable for administrators debugging in a production environment. Rationale: core dumps may contain sensitive in-memory data like password hashes or keys. An attacker could potentially exploit this to gain access to such data. Page 159 Internal Only - General Audit: 1. Run the following script to verify fs.suid_dumpable is set to 0 in the running configuration: # sysctl fs.suid_dumpable Verify output is: fs.suid_dumpable = 0 2. Run the following script to verify fs.suid_dumpable is set to 0 in a sysctl conf file being used by systemd sysctl: #!/usr/bin/env bash { l_parameter_name="fs.suid_dumpable" l_grep="${l_parameter_name//./\\.}" a_output=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufwscf="$([ -f /etc/default/ufw ] && awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" l_opt="$(grep -Psoi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_ufwscf" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - UFW set: \"$l_parameter_name\" to: \"$l_option_value\" in: \"$l_file\"") while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && a_output+=(" - \"$l_parameter_name\" is set to: \"$l_option_value\" in: \"$l_file\"") done < <("$l_systemdsysctl" --cat-config | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "fs.suid_dumpable" is set to: "0" in: "/etc/sysctl.d/60- kernel_sysctl.conf" Page 160 Internal Only - General Note: • If the UFW set value is displayed, and is the correct value, this is considered a passing state. If this value is incorrect, it must be updated in the file shown in the audit script output. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to correct or comment out the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl do to system configuration changes. Remediation: 1. Review all files ending in .conf in the /etc/sysctl.d directory and comment out or remove all fs.suid_dumpable lines that are not fs.suid_dumpable=0. Example script: #!/usr/bin/env bash { l_option="fs.suid_dumpable" l_grep="${l_option//./\\.}" l_value="0" while IFS= read -r -d $'\0' l_file; do grep -Poi '\h*'"$l_option"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*kernel.yama.ptrace_scope\s*=/s/^/# /' "$l_file" done < <(find /etc/sysctl.d/ -type f -name '*.conf' -print0) } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: fs.suid_dumpable = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "fs.suid_dumpable = 0" >> /etc/sysctl.d/60- kernel_sysctl.conf 3. Run the following command to load all system configuration filles: # sysctl --system Page 161 Internal Only - General Default Value: fs.suid_dumpable = 0 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 162 Internal Only - General 1.5.4 Ensure core file size is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: core - limits the core file size hard - for enforcing hard resource limits. These limits are set by the superuser and enforced by the Kernel. The user cannot raise their requirement of system resources above such values. Rationale: Setting a hard limit on core dumps prevents users from overriding the soft variable. A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems. Audit: Run the following command to verify a hard limit for core is set to 0 for all users *: # grep -Psi -- '^\h*\*\h+hard\h+core\b' /etc/security/limits.conf /etc/security/limits.d/* Example output: /etc/security/limits.d/60-limits.conf:* hard core 0 Verify no line are returned with a value greater than 0. Remediation: 1. Run the following command to comment out any entries that include a hard value for core greater than 0 in /etc/security/limits.conf and and file in the /etc/security/limits.d/ directory. Example: # sed -ri '/^\s*[#\n\r]+\s+hard\s+core\h+([1-9][0-9]*)/s/^/# /' /etc/security/limits.conf /etc/security/limits.d/* 2. Create or edit a file in /etc/security/limits.d/ and add the following line: * hard core 0 Example: # printf '%s\n' "" "* hard core 0" >> /etc/security/limits.d/60-limits.conf Page 163 Internal Only - General Default Value: None References: 1. limits.conf(5) 2. CCI-000366 3. NIST SP 800-53 :: CM-6 b 4. NIST SP 800-53A :: CM-6.1 (iv) 5. STIG ID: RHEL-08-010673 | RULE ID: SV-230313r1069304 | CAT II 6. STIG ID: RHEL-09-213095 | RULE ID: SV-257814r991589 | CAT II 7. STIG ID: ALMA-09-044900 | RULE ID: SV-269452r1050335 | CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 164 Internal Only - General 1.5.5 Ensure prelink is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: prelink is a program that modifies ELF shared libraries and ELF dynamically linked binaries in such a way that the time needed for the dynamic linker to perform relocations at startup significantly decreases. Rationale: The prelinking feature can interfere with the operation of AIDE, because it changes binaries. Prelinking can also increase the vulnerability of the system if a malicious user is able to compromise a common library such as libc. Audit: Verify prelink is not installed: # dpkg-query -s prelink &>/dev/null && echo "prelink is installed" Nothing should be returned. Remediation: Run the following command to restore binaries to normal: # prelink -ua Uninstall prelink using the appropriate package manager or manual installation: # apt purge prelink References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 165 Internal Only - General 1.5.6 Ensure Automatic Error Reporting is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Apport Error Reporting Service automatically generates crash reports for debugging Rationale: Apport collects potentially sensitive data, such as core dumps, stack traces, and log files. They can contain passwords, credit card numbers, serial numbers, and other private material. Audit: Run the following command to verify that the Apport Error Reporting Service is not enabled: # dpkg-query -s apport &> /dev/null && grep -Psi -- '^\h*enabled\h*=\h*[^0]\b' /etc/default/apport Nothing should be returned Run the following command to verify that the apport service is not active: # systemctl is-active apport.service | grep '^active' Nothing should be returned Remediation: Edit /etc/default/apport and add or edit the enabled parameter to equal 0: enabled=0 Run the following commands to stop and mask the apport service # systemctl stop apport.service # systemctl mask apport.service - OR - Run the following command to remove the apport package: # apt purge apport Default Value: enabled=1 Page 166 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 167 Internal Only - General 1.6 Configure Command Line Warning Banners Presenting a warning message prior to the normal user login may assist in the prosecution of trespassers on the computer system. Changing some of these login banners also has the side effect of hiding OS version information and other detailed system information from attackers attempting to target specific exploits at a system. Guidelines published by the US Department of Defense require that warning messages include at least the name of the organization that owns the system, the fact that the system is subject to monitoring and that such monitoring is in compliance with local statutes, and that use of the system implies consent to such monitoring. It is important that the organization's legal counsel review the content of all messages before any system modifications are made, as these warning messages are inherently site-specific. More information (including citations of relevant case law) can be found at http://www.justice.gov/criminal/cybercrime/ The /etc/motd, /etc/issue, and /etc/issue.net files govern warning banners for standard command line logins for both local and remote users. Note: The text provided in the remediation actions for these items is intended as an example only. Please edit to include the specific text for your organization as approved by your legal department. Page 168 Internal Only - General 1.6.1 Ensure /etc/motd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Page 169 Internal Only - General Audit: Run the following script to verify MOTD files do not contain system information: #!/usr/bin/env bash { l_output="" l_output2="" a_files=() for l_file in /etc/motd{,.d/*}; do if grep -Psqi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep ^ID= /etc/os-release | cut -d= -f2 | sed -e 's/"//g')\b)" "$l_file"; then l_output2="$l_output2\n - File: \"$l_file\" includes system information" else a_files+=("$l_file") fi done if [ "${#a_files[@]}" -gt 0 ]; then echo -e "\n- ** Please review the following files and verify their contents follow local site policy **\n" printf '%s\n' "${a_files[@]}" elif [ -z "$l_output2" ]; then echo -e "- ** No MOTD files with any size were found. Please verify this conforms to local site policy ** -" fi if [ -z "$l_output2" ]; then l_output=" - No MOTD files include system information" echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n" fi } Review any files returned and verify that they follow local site policy Page 170 Internal Only - General Remediation: Edit the file found in /etc/motd.d/* with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform - OR - - IF - the motd is not used, this file can be removed. Run the following command to remove the motd file: # rm /etc/motd Run the following script and review and/or update all returned files' contents to: • Remove all system information (\v, \r; \m, \s) • Remove any refence to the operating system • Ensure contents follow local site policy #!/usr/bin/env bash { a_files=() for l_file in /etc/motd{,.d/*}; do if grep -Psqi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep ^ID= /etc/os-release | cut -d= -f2 | sed -e 's/"//g')\b)" "$l_file"; then echo -e "\n - File: \"$l_file\" includes system information. Edit this file to remove these entries" else a_files+=("$l_file") fi done if [ "${#a_files[@]}" -gt 0 ]; then echo -e "\n- ** Please review the following files and verify their contents follow local site policy **\n" printf '%s\n' "${a_files[@]}" fi } References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 171 Internal Only - General 1.6.2 Ensure /etc/issue is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue file are displayed to users prior to login for local terminals. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version - or the operating system's name Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Audit: Run the following command and verify that the contents match site policy: # cat /etc/issue Run the following command and verify no results are returned: # grep -Psi "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut -d= - f2 | sed -e 's/"//g')\b)" /etc/issue Remediation: Edit the /etc/issue file with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # echo "Authorized users only. All activity may be monitored and reported." > /etc/issue References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 Page 172 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 173 Internal Only - General 1.6.3 Ensure /etc/issue.net is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue.net file are displayed to users prior to login for remote connections from configured services. Unix-based systems have typically displayed information about the OS release and patch level upon logging in to the system. This information can be useful to developers who are developing software for a particular OS platform. If mingetty(8) supports the following options, they display operating system information: \m - machine architecture \r - operating system release \s - operating system name \v - operating system version Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Displaying OS and patch level information in login banners also has the side effect of providing detailed system information to attackers attempting to target specific exploits of a system. Authorized users can easily get this information by running the " uname -a " command once they have logged in. Audit: Run the following command and verify that the contents match site policy: # cat /etc/issue.net Run the following command and verify no results are returned: # grep -Psi "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut -d= - f2 | sed -e 's/"//g')\b)" /etc/issue.net Remediation: Edit the /etc/issue.net file with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # echo "Authorized users only. All activity may be monitored and reported." > /etc/issue.net References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-1, CM-3 Page 174 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 175 Internal Only - General 1.6.4 Ensure access to /etc/motd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/motd file are displayed to users after login and function as a message of the day for authenticated users. Rationale: - IF - the /etc/motd file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify that if /etc/motd exists, Access is 644 or more restrictive, Uid and Gid are both 0/root: # [ -e /etc/motd ] && stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/motd Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) -- OR -- Nothing is returned Remediation: Run the following commands to set mode, owner, and group on /etc/motd: # chown root:root $(readlink -e /etc/motd) # chmod u-x,go-wx $(readlink -e /etc/motd) - OR - Run the following command to remove the /etc/motd file: # rm /etc/motd References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 176 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 177 Internal Only - General 1.6.5 Ensure access to /etc/issue is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue file are displayed to users prior to login for local terminals. Rationale: - IF - the /etc/issue file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify Access is 644 or more restrictive and Uid and Gid are both 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/issue Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) Remediation: Run the following commands to set mode, owner, and group on /etc/issue: # chown root:root $(readlink -e /etc/issue) # chmod u-x,go-wx $(readlink -e /etc/issue) Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 178 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 179 Internal Only - General 1.6.6 Ensure access to /etc/issue.net is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The contents of the /etc/issue.net file are displayed to users prior to login for remote connections from configured services. Rationale: - IF - the /etc/issue.net file does not have the correct access configured, it could be modified by unauthorized users with incorrect or misleading information. Audit: Run the following command and verify Access is 644 or more restrictive and Uid and Gid are both 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/issue.net Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to set mode, owner, and group on /etc/issue.net: # chown root:root $(readlink -e /etc/issue.net) # chmod u-x,go-wx $(readlink -e /etc/issue.net) Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 180 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 181 Internal Only - General 1.7 Configure GNOME Display Manager The GNOME Display Manager (GDM) is a program that manages graphical display servers and handles graphical user logins. This subsection requires user profiles to already exist on the system. A profile is a list of configuration databases. Sample profile: user-db:user system-db:local system-db:site Configuring a single user and multiple system databases allows for layering of preferences. Settings from the user database file take precedence over the settings in the local database file, and the local database file in turn takes precedence over the site database file. Note: • - IF - GDM is not installed on the system, this section can be skipped • The Remediation Procedure commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. Page 182 Internal Only - General 1.7.1 Ensure GDM is removed (Automated) Profile Applicability: • Level 2 - Server Description: The GNOME Display Manager (GDM) is a program that manages graphical display servers and handles graphical user logins. Rationale: If a Graphical User Interface (GUI) is not required, it should be removed to reduce the attack surface of the system. Impact: Removing the GNOME Display manager will remove the Graphical User Interface (GUI) from the system. Audit: Run the following command and verify gdm3 is not installed: # dpkg-query -s gdm3 &>/dev/null && echo "gdm3 is installed" Nothing should be returned Remediation: Run the following commands to uninstall gdm3 and remove unused dependencies: # apt purge gdm3 # apt autoremove gdm3 References: 1. NIST SP 800-53 Rev. 5: CM-11 Page 183 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 184 Internal Only - General 1.7.2 Ensure GDM login banner is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GDM is the GNOME Display Manager which handles graphical login for GNOME based systems. Rationale: Warning messages inform users who are attempting to login to the system of their legal status regarding the system and must include the name of the organization that owns the system and any monitoring policies that are in place. Audit: Run the following command to verify that a user profile exists: # grep -Psi "user-db|system-db" /etc/dconf/profile/*/* /etc/dconf/profile/gdm:user-db:user /etc/dconf/profile/gdm:system-db:local Run the following commands to verify that the text banner on the login screen is enabled and set: # gsettings get org.gnome.login-screen banner-message-enable true # gsettings get org.gnome.login-screen banner-message-text 'Authorized uses only. All activity may be monitored and reported' Page 185 Internal Only - General Remediation: - IF - A user profile is already created run the following commands to set and enable the text banner message on the login screen: # gsettings set org.gnome.login-screen banner-message-text 'Authorized uses only. All activity may be monitored and reported' # gsettings set org.gnome.login-screen banner-message-enable true Note: • banner-message-text may be set in accordance with local site policy • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. - OR/IF - A user profile does not exist: 1. Create or edit the gdm profile in the /etc/dconf/profile/gdm with the following lines: user-db:user system-db:gdm file-db:/usr/share/gdm/greeter-dconf-defaults Note: gdm is the name of a dconf database. 2. Create a gdm keyfile for machine-wide settings in /etc/dconf/db/gdm.d/01- banner-message: [org/gnome/login-screen] banner-message-enable=true banner-message-text='Type the banner message here.' 3. Update the system databases # dconf update Note: • Users must log out and back in again before the system-wide settings take effect. • There is no character limit for the banner message. gnome-shell autodetects longer stretches of text and enters two column mode. • The banner message cannot be read from an external file. Default Value: disabled Page 186 Internal Only - General References: 1. https://help.gnome.org/admin/system-admin-guide/stable/login-banner.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Additional Information: Additional options and sections may appear in the /etc/dconf/db/gdm.d/01-banner- message file. If a different GUI login service is in use, consult your documentation and apply an equivalent banner. Page 187 Internal Only - General 1.7.3 Ensure GDM disable-user-list option is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GDM is the GNOME Display Manager which handles graphical login for GNOME based systems. The disable-user-list option controls if a list of users is displayed on the login screen Rationale: Displaying the user list eliminates half of the Userid/Password equation that an unauthorized person would need to log on. Audit: Run the following command to verify that a user profile exists: # grep -Psi "user-db|system-db" /etc/dconf/profile/*/* /etc/dconf/profile/local:user-db:user /etc/dconf/profile/local:system-db:local Run the following command and to verify that the disable-user-list option is enabled: # gsettings get org.gnome.login-screen disable-user-list true Page 188 Internal Only - General Remediation: - IF - A user profile exists run the following command to enable the disable-user- list: # gsettings set org.gnome.login-screen disable-user-list true Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. - OR/IF - A user profile does not exist: 1. Create or edit the gdm profile in /etc/dconf/profile/gdm with the following lines: user-db:user system-db:gdm file-db:/usr/share/gdm/greeter-dconf-defaults Note: gdm is the name of a dconf database. 2. Create a gdm keyfile for machine-wide settings in /etc/dconf/db/gdm.d/00- login-screen: [org/gnome/login-screen] # Do not show the user list disable-user-list=true 3. Update the system databases: # dconf update Note: When the user profile is created or changed, the user will need to log out and log in again before the changes will be applied. Default Value: false References: 1. https://help.gnome.org/admin/system-admin-guide/stable/login-userlist- disable.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 189 Internal Only - General Additional Information: If a different GUI login service is in use and required on the system, consult your documentation to disable displaying the user list Page 190 Internal Only - General 1.7.4 Ensure GDM screen locks when the user is idle (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GNOME Desktop Manager can make the screen lock automatically whenever the user is idle for some amount of time. Rationale: Setting a lock-out value reduces the window of opportunity for unauthorized user access to another user's session that has been left unattended. Audit: Run the following command to verify that a user profile exists: # grep -Psi "user-db|system-db" /etc/dconf/profile/*/* /etc/dconf/profile/local:user-db:user /etc/dconf/profile/local:system-db:local Run the following commands to verify that the screen locks when the user is idle: # gsettings get org.gnome.desktop.screensaver lock-delay uint32 5 # gsettings get org.gnome.desktop.session idle-delay uint32 900 # gsettings get org.gnome.desktop.screensaver lock-enabled true Notes: • lock-delay=uint32 {n} - should be 5 seconds or less and follow local site policy • idle-delay=uint32 {n} - Should be 900 seconds (15 minutes) or less, not 0 (disabled) and follow local site policy • lock-enabled - must be set to true for screen locks to lock when the user is idle Page 191 Internal Only - General Remediation: - IF - A user profile is already created run the following commands to enable screen locks when the user is idle: # gsettings set org.gnome.desktop.screensaver lock-delay 5 # gsettings set org.gnome.desktop.session idle-delay 900 # gsettings set org.gnome.desktop.screensaver lock-enabled true Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. - OR/IF- A user profile does not exist: 1. Create or edit the user profile in the /etc/dconf/profile/ and verify it includes the following: user-db:user system-db:{NAME_OF_DCONF_DATABASE} Note: local is the name of a dconf database used in the examples. 2. Create the directory /etc/dconf/db/local.d/ if it doesn't already exist: 3. Create the key file /etc/dconf/db/local.d/00-screensaver to provide information for the local database: Example key file: # Specify the dconf path [org/gnome/desktop/session] # Number of seconds of inactivity before the screen goes blank # Set to 0 seconds if you want to deactivate the screensaver. idle-delay=uint32 180 # Specify the dconf path [org/gnome/desktop/screensaver] # Number of seconds after the screen is blank before locking the screen lock-delay=uint32 0 # Ensure screen locks after inactivity lock-enabled=true Note: You must include the uint32 along with the integer key values as shown. 4. Run the following command to update the system databases: # dconf update Page 192 Internal Only - General 5. Users must log out and back in again before the system-wide settings take effect. References: 1. https://help.gnome.org/admin/system-admin-guide/stable/desktop- lockscreen.html.en CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 193 Internal Only - General 1.7.5 Ensure GDM screen locks cannot be overridden (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: GNOME Desktop Manager can lock down specific settings by using the lockdown mode in dconf to prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: Setting a lock-out value reduces the window of opportunity for unauthorized user access to another user's session that has been left unattended. Without locking down the system settings, user settings take precedence over the system settings. Audit: Run the following commands to verify that the screen lock cannot be overridden: # grep -Psi "idle-delay|lock-delay|lock-enabled" /etc/dconf/db/*/locks/* /org/gnome/desktop/session/idle-delay /org/gnome/desktop/screensaver/lock-delay /org/gnome/desktop/screensaver/lock-enabled Page 194 Internal Only - General Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-screensaver with the following content: # Lock desktop screensaver settings /org/gnome/desktop/session/idle-delay /org/gnome/desktop/screensaver/lock-delay /org/gnome/desktop/screensaver/lock-enabled 2. Update the system databases: # dconf update Note: • A user profile must exist in order to apply locks. If a user profile does not exist review the remediation steps in the previous recommendation. • Users must log out and back in again before the system-wide settings take effect. References: 1. https://help.gnome.org/admin/system-admin-guide/stable/desktop- lockscreen.html.en 2. https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en 3. NIST SP 800-53 Rev. 5: CM-11 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 195 Internal Only - General 1.7.6 Ensure GDM automatic mounting of removable media is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: By default GNOME automatically mounts removable media when inserted as a convenience to the user. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users. If your organization allows the use of portable storage or media on workstations and physical access controls to workstations is considered adequate there is little value add in turning off automounting. Audit: Run the following command to verify that a user profile exists: # grep -Psi "user-db|system-db" /etc/dconf/profile/*/* /etc/dconf/profile/local:user-db:user /etc/dconf/profile/local:system-db:local Run the following commands to verify automatic mounting is disabled: # gsettings get org.gnome.desktop.media-handling automount false # gsettings get org.gnome.desktop.media-handling automount-open false Page 196 Internal Only - General Remediation: - IF - A user profile exists run the following commands to ensure automatic mounting is disabled: # gsettings set org.gnome.desktop.media-handling automount false # gsettings set org.gnome.desktop.media-handling automount-open false Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. - OR/IF - A user profile does not exist: 1. Create a file /etc/dconf/db/local.d/00-media-automount with following content: [org/gnome/desktop/media-handling] automount=false automount-open=false 2. After creating the file, apply the changes using below command : # dconf update Note: Users must log out and back in again before the system-wide settings take effect. References: 1. https://access.redhat.com/solutions/20107 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 197 Internal Only - General 1.7.7 Ensure GDM disabling automatic mounting of removable media is not overridden (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: By default GNOME automatically mounts removable media when inserted as a convenience to the user. By using the lockdown mode in dconf, you can prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users Audit: Run the following command to verify automount=false and automount-open=false is correctly configured to ensure automatic mounting of removable media is not overridden: # grep -Psi "automount" /etc/dconf/db/*/locks/* /etc/dconf/db/local.d/locks/00-media-automount:automount=false /etc/dconf/db/local.d/locks/00-media-automount:automount-open=false Page 198 Internal Only - General Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-media-automount with the following content: [org/gnome/desktop/media-handling] automount=false automount-open=false 2. Update the systems databases: # dconf update Note: • A user profile must exist in order to apply locks. If a user profile does not exist review the remediation steps in the previous recommendation. • Users must log out and back in again before the system-wide settings take effect. References: 1. https://help.gnome.org/admin/system-admin-guide/stable/dconf-lockdown.html.en 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 3. https://manpages.ubuntu.com/manpages/trusty/man1/gsettings.1.html 4. https://access.redhat.com/solutions/20107 Page 199 Internal Only - General 1.7.8 Ensure GDM autorun-never is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The autorun-never setting allows the GNOME Desktop Display Manager to disable autorun through GDM. Rationale: Malware on removable media may taking advantage of Autorun features when the media is inserted into a system and execute. Audit: Run the following command to verify that a user profile exists: # grep -Psi "user-db|system-db" /etc/dconf/profile/*/* /etc/dconf/profile/local:user-db:user /etc/dconf/profile/local:system-db:local Run the following command to verify that autorun-never is set to true for GDM: # gsettings get org.gnome.desktop.media-handling autorun-never true Page 200 Internal Only - General Remediation: - IF - A user profile exist run the following command to set autorun-never to true for GDM users: # gsettings set org.gnome.desktop.media-handling autorun-never true Note: • gsettings commands in this section MUST be done from a command window on a graphical desktop or an error will be returned. • The system must be restarted after all gsettings configurations have been set in order for CIS-CAT Assessor to appropriately assess. - OR/IF - A user profile does not exist: 1. create the file /etc/dconf/db/local.d/locks/00-media-autorun with the following content: [org/gnome/desktop/media-handling] autorun-never=true 2. Update the systems databases: # dconf update Note: Users must log out and back in again before the system-wide settings take effect. Default Value: false References: 1. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 201 Internal Only - General 1.7.9 Ensure GDM autorun-never is not overridden (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The autorun-never setting allows the GNOME Desktop Display Manager to disable autorun through GDM. By using the lockdown mode in dconf, you can prevent users from changing specific settings. To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory. Rationale: Malware on removable media may taking advantage of Autorun features when the media is inserted into a system and execute. Audit: Run the following command to verify that autorun-never=true cannot be overridden: # grep -Psi "autorun-never" /etc/dconf/db/*/locks/* /etc/dconf/db/local.d/locks/00-media-autorun:autorun-never=true Remediation: 1. To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/00-media-autorun with the following content: [org/gnome/desktop/media-handling] autorun-never=true 2. Update the systems databases: # dconf update Note: • A user profile must exist in order to apply locks. If a user profile does not exist review the remediation steps in the previous recommendation. • Users must log out and back in again before the system-wide settings take effect. Page 202 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 203 Internal Only - General 1.7.10 Ensure XDMCP is not enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: X Display Manager Control Protocol (XDMCP) is designed to provide authenticated access to display management services for remote displays Rationale: XDMCP is inherently insecure. • XDMCP is not a ciphered protocol. This may allow an attacker to capture keystrokes entered by a user • XDMCP is vulnerable to man-in-the-middle attacks. This may allow an attacker to steal the credentials of legitimate users by impersonating the XDMCP server. Audit: Run the following script and verify the output: #!/usr/bin/env bash { while IFS= read -r l_file; do awk '/\[xdmcp\]/{ f = 1;next } /\[/{ f = 0 } f {if (/^\s*Enable\s*=\s*true/) print "The file: \"'"$l_file"'\" includes: \"" $0 "\" in the \"[xdmcp]\" block"}' "$l_file" done < <(grep -Psil -- '^\h*\[xdmcp\]' /etc/{gdm3,gdm}/{custom,daemon}.conf) } Nothing should be returned Page 204 Internal Only - General Remediation: Edit all files returned by the audit and remove or comment out the Enable=true line in the [xdmcp] block: Example file: # GDM configuration storage # # See /usr/share/gdm/gdm.schemas for a list of available options. [daemon] # Uncomment the line below to force the login screen to use Xorg #WaylandEnable=false # Enabling automatic login # AutomaticLoginEnable = true # AutomaticLogin = user1 # Enabling timed login # TimedLoginEnable = true # TimedLogin = user1 # TimedLoginDelay = 10 [security] [xdmcp] # Enable=true <- **This line should be removed or commented out** [chooser] [debug] # Uncomment the line below to turn on debugging # More verbose logs # Additionally lets the X server dump core if it crashes # Enable=true Default Value: false References: 1. NIST SP 800-53 Rev. 5: SI-4 Page 205 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 206 Internal Only - General 1.7.11 Ensure Xwayland is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Xwayland is a compatibility layer that allows legacy X11 applications to run within a Wayland environment. It's effectively an X server that runs as a Wayland client, enabling existing X11 software to be displayed on a Wayland compositor. Rationale: Wayland's security benefits from not relying on X11's network listener. Without X11, there's no network listener, making it harder for malicious actors to exploit vulnerabilities in X11. However, enabling Xwayland (running X11 applications on Wayland) introduces X11's security concerns. All X vulnerabilities apply to Xwayland, including keylogging, but they only affect X windows and interactions with them. Malware can potentially exploit Xwayland vulnerabilities to keylog or intercept other input events Impact: Many applications haven't been ported to Wayland yet, and Xwayland makes it possible to run these applications without requiring a full switch back to X11. Disabling Xwayland functionality may cause these applications to fail. Audit: Run the following command to verify Xwayland is not enabled: # sed -n '/\[daemon\]/,/\[/p' /etc/gdm/custom.conf | grep -Psi '^\h*waylandenable\b' Verify output includes: WaylandEnable=false Page 207 Internal Only - General Remediation: Edit the file /etc/gdm/custom.conf and uncomment or add the following line in the [daemon] block: WaylandEnable=false Example: # GDM configuration storage [daemon] WaylandEnable=false [security] [xdmcp] [chooser] [debug] # Uncomment the line below to turn on debugging #Enable=true Default Value: Enabled CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 208 Internal Only - General 2 Services While applying system updates and patches helps correct known vulnerabilities, one of the best ways to protect the system against as yet unreported vulnerabilities is to disable all services that are not required for normal system operation. This prevents the exploitation of vulnerabilities discovered at a later date. If a service is not enabled, it cannot be exploited. The actions in this section of the document provide guidance on some services which can be safely disabled and under which circumstances, greatly reducing the number of possible threats to the resulting system. Additionally, some services which should remain enabled but with secure configuration are covered as well as insecure service clients. Page 209 Internal Only - General 2.1 Configure Server Services This section describes services that are installed on systems that specifically need to run these services. If any of these services are not required, it is recommended that the package be removed. - IF - the package is required for a dependency: • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy • Stop and mask the service and/or socket to reduce the potential attack surface The following commands can be used to stop and mask the service and socket: # systemctl stop .socket .service # systemctl mask .socket .service Note: This should not be considered a comprehensive list of services not required for normal system operation. You may wish to consider additions to those listed here for your environment Page 210 Internal Only - General 2.1.1 Ensure autofs services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: autofs allows automatic mounting of devices, typically including CD/DVDs and USB drives. Rationale: With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in the filesystem even if they lacked permissions to mount it themselves. Impact: The use of portable hard drives is very common for workstation users. If your organization allows the use of portable storage or media on workstations and physical access controls to workstations is considered adequate there is little value add in turning off automounting. There may be packages that are dependent on the autofs package. If the autofs package is removed, these dependent packages will be removed as well. Before removing the autofs package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the autofs.service leaving the autofs package installed. Page 211 Internal Only - General Audit: As a preference autofs should not be installed unless other packages depend on it. Run the following command to verify autofs is not installed: # dpkg-query -s autofs &>/dev/null && echo "autofs is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify autofs.service is not enabled: # systemctl is-enabled autofs.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the autofs.service is not active: # systemctl is-active autofs.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop autofs.service and remove the autofs package: # systemctl stop autofs.service # apt purge autofs - OR - - IF - the autofs package is required as a dependency: Run the following commands to stop and mask autofs.service: # systemctl stop autofs.service # systemctl mask autofs.service References: 1. NIST SP 800-53 Rev. 5: SI-3, MP-7 2. RHEL 8 STIG Vul ID: V-230502 3. RHEL 8 STIG Rule ID: SV-230502r627750 Page 212 Internal Only - General Additional Information: This control should align with the tolerance of the use of portable drives and optical media in the organization. On a server, requiring an admin to manually mount media can be part of defense-in-depth to reduce the risk of unapproved software or information being introduced or proprietary software or information being exfiltrated. If admins commonly use flash drives and Server access has sufficient physical controls, requiring manual mounting may not increase security. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 10.3 Disable Autorun and Autoplay for Removable v8 Media ● ● ● Disable autorun and autoplay auto-execute functionality for removable media. v7 8.5 Configure Devices Not To Auto-run Content ● ● ● Configure devices to not auto-run content from removable media. Page 213 Internal Only - General 2.1.2 Ensure avahi daemon services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: Avahi is a free zeroconf implementation, including a system for multicast DNS/DNS-SD service discovery. Avahi allows programs to publish and discover services and hosts running on a local network with no specific configuration. For example, a user can plug a computer into a network and Avahi automatically finds printers to print to, files to look at and people to talk to, as well as network services running on the machine. Rationale: Automatic discovery of network services is not normally required for system functionality. It is recommended to remove this package to reduce the potential attack surface. Impact: There may be packages that are dependent on the avahi package. If the avahi package is removed, these dependent packages will be removed as well. Before removing the avahi package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the avahi-daemon.socket and avahi-daemon.service leaving the avahi package installed. Page 214 Internal Only - General Audit: Run the following command to verify avahi-daemon is not installed: # dpkg-query -s avahi-daemon &>/dev/null && echo "avahi-daemon is installed" Nothing should be returned. - OR - - IF - the avahi package is required as a dependency: Run the following command to verify avahi-daemon.socket and avahi- daemon.service are not enabled: # systemctl is-enabled avahi-daemon.socket avahi-daemon.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify avahi-daemon.socket and avahi- daemon.service are not active: # systemctl is-active avahi-daemon.socket avahi-daemon.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop avahi-daemon.socket and avahi- daemon.service, and remove the avahi-daemon package: # systemctl stop avahi-daemon.socket avahi-daemon.service # apt purge avahi-daemon - OR - - IF - the avahi-daemon package is required as a dependency: Run the following commands to stop and mask the avahi-daemon.socket and avahi- daemon.service: # systemctl stop avahi-daemon.socket avahi-daemon.service # systemctl mask avahi-daemon.socket avahi-daemon.service References: 1. NIST SP 800-53 Rev. 5: SI-4 Page 215 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 216 Internal Only - General 2.1.3 Ensure dhcp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Dynamic Host Configuration Protocol (DHCP) is a service that allows machines to be dynamically assigned IP addresses. There are two versions of the DHCP protocol DHCPv4 and DHCPv6. At startup the server may be started for one or the other via the -4 or -6 arguments. Rationale: Unless a system is specifically set up to act as a DHCP server, it is recommended that this package be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the isc-dhcp-server package. If the isc-dhcp-server package is removed, these dependent packages will be removed as well. Before removing the isc-dhcp-server package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the isc-dhcp-server.service and isc-dhcp-server6.service leaving the isc-dhcp-server package installed. Page 217 Internal Only - General Audit: Run the following commands to verify isc-dhcp-server is not installed: # dpkg-query -s isc-dhcp-server &>/dev/null && echo "isc-dhcp-server is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify isc-dhcp-server.service and isc-dhcp- server6.service are not enabled: # systemctl is-enabled isc-dhcp-server.service isc-dhcp-server6.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify isc-dhcp-server.service and isc-dhcp- server6.service are not active: # systemctl is-active isc-dhcp-server.service isc-dhcp-server6.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop isc-dhcp-server.service and isc-dhcp- server6.service and remove the isc-dhcp-server package: # systemctl stop isc-dhcp-server.service isc-dhcp-server6.service # apt purge isc-dhcp-server - OR - - IF - the isc-dhcp-server package is required as a dependency: Run the following commands to stop and mask isc-dhcp-server.service and isc- dhcp-server6.service: # systemctl stop isc-dhcp-server.service isc-dhcp-server6.service # systemctl mask isc-dhcp-server isc-dhcp-server6.service References: 1. More detailed documentation on DHCP is available at http://www.isc.org/software/dhcp. 2. NIST SP 800-53 Rev. 5: CM-7 Page 218 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 219 Internal Only - General 2.1.4 Ensure dns server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Domain Name System (DNS) is a hierarchical naming system that maps names to IP addresses for computers, services and other resources connected to a network. Note: bind9 is the package and bind.service is the alias for named.service. Rationale: Unless a system is specifically designated to act as a DNS server, it is recommended that the package be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the bind9 package. If the bind9 package is removed, these dependent packages will be removed as well. Before removing the bind9 package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask named.service leaving the bind9 package installed. Audit: Run the following command to verify bind9 is not installed: # dpkg-query -s bind9 &>/dev/null && echo "bind9 is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify named.service is not enabled: # systemctl is-enabled named.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the named.service is not active: # systemctl is-active named.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 220 Internal Only - General Remediation: Run the following commands to stop named.service and remove the bind9 package: # systemctl stop named.service # apt purge bind9 - OR - - IF - the bind9 package is required as a dependency: Run the following commands to stop and mask bind9.service: # systemctl stop named.service # systemctl mask named.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 221 Internal Only - General 2.1.5 Ensure dnsmasq services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: dnsmasq is a lightweight tool that provides DNS caching, DNS forwarding and DHCP (Dynamic Host Configuration Protocol) services. Rationale: Unless a system is specifically designated to act as a DNS caching, DNS forwarding and/or DHCP server, it is recommended that the package be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the dnsmasq package. If the dnsmasq package is removed, these dependent packages will be removed as well. Before removing the dnsmasq package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the dnsmasq.service leaving the dnsmasq package installed. Audit: Run one of the following commands to verify dnsmasq is not installed: # dpkg-query -s dnsmasq &>/dev/null && echo "dnsmasq is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify dnsmasq.service is not enabled: # systemctl is-enabled dnsmasq.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the dnsmasq.service is not active: # systemctl is-active dnsmasq.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 222 Internal Only - General Remediation: Run the following commands to stop dnsmasq.service and remove dnsmasq package: # systemctl stop dnsmasq.service # apt purge dnsmasq - OR - - IF - the dnsmasq package is required as a dependency: Run the following commands to stop and mask the dnsmasq.service: # systemctl stop dnsmasq.service # systemctl mask dnsmasq.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 223 Internal Only - General 2.1.6 Ensure ftp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The File Transfer Protocol (FTP) provides networked computers with the ability to transfer files. vsftpd is the Very Secure File Transfer Protocol Daemon. Rationale: FTP does not protect the confidentiality of data or authentication credentials. It is recommended SFTP be used if file transfer is required. Unless there is a need to run the system as a FTP server (for example, to allow anonymous downloads), it is recommended that the package be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the vsftpd package. If the vsftpd package is removed, these dependent packages will be removed as well. Before removing the vsftpd package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the vsftpd.service leaving the vsftpd package installed. Page 224 Internal Only - General Audit: Run the following command to verify vsftpd is not installed: # dpkg-query -l | awk '{print $2}' | grep -E '^ftp|^tnftp' &>/dev/null && echo "ftp is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify vsftpd service is not enabled: # systemctl is-enabled vsftpd.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify the vsftpd service is not active: # systemctl is-active vsftpd.service 2>/dev/null | grep '^active' Nothing should be returned. Note: • Other ftp server packages may exist. They should also be audited, if not required and authorized by local site policy • If the package is required for a dependency: o Ensure the dependent package is approved by local site policy o Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop vsftpd.service and remove the vsftpd package: # systemctl stop vsftpd.service # apt purge vsftpd - OR - - IF - the vsftpd package is required as a dependency: Run the following commands to stop and mask the vsftpd.service: # systemctl stop vsftpd.service # systemctl mask vsftpd.service Note: Other ftp server packages may exist. If not required and authorized by local site policy, they should also be removed. If the package is required for a dependency, the service should be stopped and masked. References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 225 Internal Only - General Additional Information: Additional FTP servers also exist and should be audited. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 226 Internal Only - General 2.1.7 Ensure ldap server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP server, it is recommended that the software be removed to reduce the potential attack surface. Impact: There may be packages that are dependent on the slapd package. If the slapd package is removed, these dependent packages will be removed as well. Before removing the slapd package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the slapd.service leaving the slapd package installed. Audit: Run the following command to verify slapd is not installed: # dpkg-query -s slapd &>/dev/null && echo "slapd is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify slapd.service is not enabled: # systemctl is-enabled slapd.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify slapd.service is not active: # systemctl is-active slapd.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 227 Internal Only - General Remediation: Run the following commands to stop slapd.service and remove the slapd package: # systemctl stop slapd.service # apt purge slapd - OR - - IF - the slapd package is required as a dependency: Run the following commands to stop and mask slapd.service: # systemctl stop slapd.service # systemctl mask slapd.service References: 1. For more detailed documentation on OpenLDAP, go to the project homepage at http://www.openldap.org. 2. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 228 Internal Only - General 2.1.8 Ensure message access server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: dovecot-imapd and dovecot-pop3d are an open source IMAP and POP3 server for Linux based systems. Rationale: Unless POP3 and/or IMAP servers are to be provided by this system, it is recommended that the package be removed to reduce the potential attack surface. Note: Several IMAP/POP3 servers exist and can use other service names. These should also be audited and the packages removed if not required. Impact: There may be packages that are dependent on dovecot-imapd and/or dovecot-pop3d packages. If dovecot-imapd and dovecot-pop3d packages are removed, these dependent packages will be removed as well. Before removing dovecot-imapd and/or dovecot-pop3d packages, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask dovecot.socket and dovecot.service leaving dovecot-imapd and/or dovecot-pop3d packages installed. Page 229 Internal Only - General Audit: Run the following command to verify dovecot-imapd and dovecot-pop3d are not installed: # dpkg-query -s dovecot-imapd &>/dev/null && echo "dovecot-imapd is installed" Nothing should be returned. # dpkg-query -s dovecot-pop3d &>/dev/null && echo "dovecot-pop3d is installed" Nothing should be returned. - OR - - IF - a package is installed and is required for dependencies: Run the following commands to verify dovecot.socket and dovecot.service are not enabled: # systemctl is-enabled dovecot.socket dovecot.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify dovecot.socket and dovecot.service are not active: # systemctl is-active dovecot.socket dovecot.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 230 Internal Only - General Remediation: Run one of the following commands to remove dovecot-imapd and dovecot-pop3d: Run the following commands to stop dovecot.socket and dovecot.service, and remove the dovecot-imapd and dovecot-pop3d packages: # systemctl stop dovecot.socket dovecot.service # apt purge dovecot-imapd dovecot-pop3d - OR - - IF - a package is installed and is required for dependencies: Run the following commands to stop and mask dovecot.socket and dovecot.service: # systemctl stop dovecot.socket dovecot.service # systemctl mask dovecot.socket dovecot.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Several IMAP/POP3 servers exist and can use other service names. courier-imap and cyrus-imap are example services that provide a mail server. These and other services should also be audited. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 231 Internal Only - General 2.1.9 Ensure network file system services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network File System (NFS) is one of the first and most widely distributed file systems in the UNIX environment. It provides the ability for systems to mount file systems of other servers through the network. Rationale: If the system does not export NFS shares, it is recommended that the nfs-kernel- server package be removed to reduce the remote attack surface. Impact: There may be packages that are dependent on the nfs-kernel-server package. If the nfs-kernel-server package is removed, these dependent packages will be removed as well. Before removing the nfs-kernel-server package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the nfs-server.service leaving the nfs-kernel-server package installed. Audit: Run the following command to verify nfs-kernel-server is not installed: # dpkg-query -s nfs-kernel-server &>/dev/null && echo "nfs-kernel-server is installed" Nothing should be returned. - OR - - IF - package is required for dependencies: Run the following command to verify that the nfs-server.service is not enabled: # systemctl is-enabled nfs-server.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the nfs-server.service is not active: # systemctl is-active nfs-server.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 232 Internal Only - General Remediation: Run the following command to stop nfs-server.service and remove nfs-kernel- server package: # systemctl stop nfs-server.service # apt purge nfs-kernel-server - OR - - IF - the nfs-kernel-server package is required as a dependency: Run the following commands to stop and mask the nfs-server.service: # systemctl stop nfs-server.service # systemctl mask nfs-server.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 233 Internal Only - General 2.1.10 Ensure nis server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network Information Service (NIS) (formally known as Yellow Pages) is a client- server directory service protocol for distributing system configuration files. The NIS server is a collection of programs that allow for the distribution of configuration files. The NIS client (ypbind) was used to bind a machine to an NIS server and receive the distributed configuration files. Rationale: ypserv.service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that ypserv.service be removed and other, more secure services be used Impact: There may be packages that are dependent on the ypserv package. If the ypserv package is removed, these dependent packages will be removed as well. Before removing the ypserv package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the ypserv.service leaving the ypserv package installed. Page 234 Internal Only - General Audit: Run the following command to verify ypserv is not installed: # dpkg-query -s ypserv &>/dev/null && echo "ypserv is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify ypserv.service is not enabled: # systemctl is-enabled ypserv.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify ypserv.service is not active: # systemctl is-active ypserv.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop ypserv.service and remove ypserv package: # systemctl stop ypserv.service # apt purge ypserv - OR - - IF - the ypserv package is required as a dependency: Run the following commands to stop and mask ypserv.service: # systemctl stop ypserv.service # systemctl mask ypserv.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 235 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 236 Internal Only - General 2.1.11 Ensure print server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: The Common Unix Print System (CUPS) provides the ability to print to both local and network printers. A system running CUPS can also accept print jobs from remote systems and print them to local printers. It also provides a web based remote administration capability. Rationale: If the system does not need to print jobs or accept print jobs from other systems, it is recommended that CUPS be removed to reduce the potential attack surface. Impact: Removing the cups package, or disabling cups.socket and/or cups.service will prevent printing from the system, a common task for workstation systems. There may be packages that are dependent on the cups package. If the cups package is removed, these dependent packages will be removed as well. Before removing the cups package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask cups.socket and cups.service leaving the cups package installed. Page 237 Internal Only - General Audit: Run the following command to verify cups is not Installed: # dpkg-query -s cups &>/dev/null && echo "cups is installed" Nothing should be returned. - OR - - IF - the cups package is required as a dependency: Run the following command to verify the cups.socket and cups.service are not enabled: # systemctl is-enabled cups.socket cups.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the cups.socket and cups.service are not active: # systemctl is-active cups.socket cups.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop cups.socket and cups.service, and remove the cups package: # systemctl stop cups.socket cups.service # apt purge cups - OR - - IF - the cups package is required as a dependency: Run the following commands to stop and mask the cups.socket and cups.service: # systemctl stop cups.socket cups.service # systemctl mask cups.socket cups.service References: 1. http://www.cups.org 2. NIST SP 800-53 Rev. 5: CM-7 Page 238 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 239 Internal Only - General 2.1.12 Ensure rpcbind services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they expect to serve. The client system then contacts rpcbind on the server with a particular RPC program number. The rpcbind.service redirects the client to the proper port number so it can communicate with the requested service. Portmapper is an RPC service, which always listens on tcp and udp 111, and is used to map other RPC services (such as nfs, nlockmgr, quotad, mountd, etc.) to their corresponding port number on the server. When a remote host makes an RPC call to that server, it first consults with portmap to determine where the RPC server is listening. Rationale: A small request (~82 bytes via UDP) sent to the Portmapper generates a large response (7x to 28x amplification), which makes it a suitable tool for DDoS attacks. If rpcbind is not required, it is recommended to remove rpcbind package to reduce the potential attack surface. Impact: Many of the libvirt packages used by Enterprise Linux virtualization, and the nfs-utils package used for The Network File System (NFS), are dependent on the rpcbind package. If the rpcbind package is removed, these dependent packages will be removed as well. Before removing the rpcbind package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the rpcbind.socket and rpcbind.service leaving the rpcbind package installed. Page 240 Internal Only - General Audit: Run the following command to verify rpcbind package is not installed: # dpkg-query -s rpcbind &>/dev/null && echo "rpcbind is installed" Nothing should be returned. - OR - - IF - the rpcbind package is required as a dependency: Run the following command to verify rpcbind.socket and rpcbind.service are not enabled: # systemctl is-enabled rpcbind.socket rpcbind.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify rpcbind.socket and rpcbind.service are not active: # systemctl is-active rpcbind.socket rpcbind.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop rpcbind.socket and rpcbind.service, and remove the rpcbind package: # systemctl stop rpcbind.socket rpcbind.service # apt purge rpcbind - OR - - IF - the rpcbind package is required as a dependency: Run the following commands to stop and mask the rpcbind.socket and rpcbind.service: # systemctl stop rpcbind.socket rpcbind.service # systemctl mask rpcbind.socket rpcbind.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 Page 241 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 242 Internal Only - General 2.1.13 Ensure rsync services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsync service can be used to synchronize files between systems over network links. Rationale: rsync.service presents a security risk as the rsync protocol is unencrypted. The rsync package should be removed to reduce the attack area of the system. Impact: There may be packages that are dependent on the rsync package. If the rsync package is removed, these dependent packages will be removed as well. Before removing the rsync package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask rsync.service leaving the rsync package installed. Audit: Run the following command to verify rsync is not installed: # dpkg-query -s rsync &>/dev/null && echo "rsync is installed" Nothing should be returned. - OR - - IF - the rsync package is required as a dependency: Run the following command to verify rsync.service is not enabled: # systemctl is-enabled rsync.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify rsync.service is not active: # systemctl is-active rsync.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 243 Internal Only - General Remediation: Run the following commands to stop rsync.service, and remove the rsync package: # systemctl stop rsync.service # apt purge rsync - OR - - IF - the rsync package is required as a dependency: Run the following commands to stop and mask rsync.service: # systemctl stop rsync.service # systemctl mask rsync.service References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 244 Internal Only - General 2.1.14 Ensure samba file server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Samba daemon allows system administrators to configure their Linux systems to share file systems and directories with Windows desktops. Samba will advertise the file systems and directories via the Server Message Block (SMB) protocol. Windows desktop users will be able to mount these directories and file systems as letter drives on their systems. Rationale: If there is no need to mount directories and file systems to Windows systems, then this service should be deleted to reduce the potential attack surface. Impact: There may be packages that are dependent on the samba package. If the samba package is removed, these dependent packages will be removed as well. Before removing the samba package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the smbd.service leaving the samba package installed. Page 245 Internal Only - General Audit: Run the following command to verify samba is not installed: # dpkg-query -s samba &>/dev/null && echo "samba is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify smbd.service is not enabled: # systemctl is-enabled smbd.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the smbd.service is not active: # systemctl is-active smbd.service 2>/dev/null | grep '^active' Nothing should be returned Remediation: Run the following commands to stop smbd.service and remove samba package: # systemctl stop smbd.service # apt purge samba - OR - - IF - the samba package is required as a dependency: Run the following commands to stop and mask the smbd.service: # systemctl stop smbd.service # systemctl mask smbd.service References: 1. NIST SP 800-53 Rev. 5: CM-6, CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 246 Internal Only - General 2.1.15 Ensure snmp services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Simple Network Management Protocol (SNMP) is a widely used protocol for monitoring the health and welfare of network equipment, computer equipment and devices like UPSs. Net-SNMP is a suite of applications used to implement SNMPv1 (RFC 1157), SNMPv2 (RFCs 1901-1908), and SNMPv3 (RFCs 3411-3418) using both IPv4 and IPv6. Support for SNMPv2 classic (a.k.a. "SNMPv2 historic" - RFCs 1441-1452) was dropped with the 4.0 release of the UCD-snmp package. The Simple Network Management Protocol (SNMP) server is used to listen for SNMP commands from an SNMP management system, execute the commands or collect the information and then send results back to the requesting system. Rationale: The SNMP server can communicate using SNMPv1, which transmits data in the clear and does not require authentication to execute commands. SNMPv3 replaces the simple/clear text password sharing used in SNMPv2 with more securely encoded parameters. If the the SNMP service is not required, the snmpd package should be removed to reduce the attack surface of the system. Note: If SNMP is required: • The server should be configured for SNMP v3 only. User Authentication and Message Encryption should be configured. • If SNMP v2 is absolutely necessary, modify the community strings' values. Impact: There may be packages that are dependent on the snmpd package. If the snmpd package is removed, these packages will be removed as well. Before removing the snmpd package, review any dependent packages to determine if they are required on the system. If a dependent package is required, stop and mask the snmpd.service leaving the snmpd package installed. Page 247 Internal Only - General Audit: Run the following command to verify snmpd is not installed: # dpkg-query -s snmpd &>/dev/null && echo "snmpd is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify the snmpd.service is not enabled: # systemctl is-enabled snmpd.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the snmpd.service is not active: # systemctl is-active snmpd.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop snmpd.service and remove the snmpd package: # systemctl stop snmpd.service # apt purge snmpd - OR - If the package is required for dependencies: Run the following commands to stop and mask the snmpd.service: # systemctl stop snmpd.service # systemctl mask snmpd.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 248 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 249 Internal Only - General 2.1.16 Ensure tftp server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Trivial File Transfer Protocol (TFTP) is a simple protocol for exchanging files between two TCP/IP machines. TFTP servers allow connections from a TFTP Client for sending and receiving files. Rationale: Unless there is a need to run the system as a TFTP server, it is recommended that the package be removed to reduce the potential attack surface. TFTP does not have built-in encryption, access control or authentication. This makes it very easy for an attacker to exploit TFTP to gain access to files Impact: TFTP is often used to provide files for network booting such as for PXE based installation of servers. There may be packages that are dependent on the tftpd-hpa package. If the tftpd- hpa package is removed, these dependent packages will be removed as well. Before removing the tftpd-hpa package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask tftpd-hpa.service leaving the tftpd-hpa package installed. Page 250 Internal Only - General Audit: Run the following command to verify tftpd-hpa is not installed: # dpkg-query -s tftpd-hpa &>/dev/null && echo "tftpd-hpa is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify tftpd-hpa.service is not enabled: # systemctl is-enabled tftpd-hpa.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the tftpd-hpa.service is not active: # systemctl is-active tftpd-hpa.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop tftpd-hpa.service, and remove the tftpd-hpa package: # systemctl stop tftpd-hpa.service # apt purge tftpd-hpa - OR - - IF - the tftpd-hpa package is required as a dependency: Run the following commands to stop and mask tftpd-hpa.service: # systemctl stop tftpd-hpa.service # systemctl mask tftpd-hpa.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 251 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 252 Internal Only - General 2.1.17 Ensure web proxy server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Squid is a standard proxy server used in many distributions and environments. Rationale: Unless a system is specifically set up to act as a proxy server, it is recommended that the squid package be removed to reduce the potential attack surface. Note: Several HTTP proxy servers exist. These should be checked and removed unless required. Impact: There may be packages that are dependent on the squid package. If the squid package is removed, these dependent packages will be removed as well. Before removing the squid package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the squid.service leaving the squid package installed. Audit: Run the following command to verify squid is not installed: # dpkg-query -s squid &>/dev/null && echo "squid is installed" Nothing should be returned. - OR - - IF - the package is required for dependencies: Run the following command to verify squid.service is not enabled: # systemctl is-enabled squid.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify the squid.service is not active: # systemctl is-active squid.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Page 253 Internal Only - General Remediation: Run the following commands to stop squid.service and remove the squid package: # systemctl stop squid.service # apt purge squid - OR - If the squid package is required as a dependency: Run the following commands to stop and mask the squid.service: # systemctl stop squid.service # systemctl mask squid.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Several HTTP proxy servers exist. These and other services should be checked CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 254 Internal Only - General 2.1.18 Ensure web server services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Web servers provide the ability to host web site content. Rationale: Unless there is a local site approved requirement to run a web server service on the system, web server packages should be removed to reduce the potential attack surface. Impact: Removal of a web server's package, or changing the state of its service and/or socket, will prevent the server from hosting web services. - IF - a web server package is required for a dependency, any related service or socket should be stopped and masked. Note: If the remediation steps to mask a service are followed and that package is not installed on the system, the service and/or socket will still be masked. If the package is installed due to an approved requirement to host a web server, the associated service and/or socket would need to be unmasked before it could be enabled and/or started. Page 255 Internal Only - General Audit: Run the following command to verify apache2 is not installed: # dpkg-query -s apache2 &>/dev/null && echo "apache2 is installed" Nothing should be returned. Run the following command to verify nginx is not installed: # dpkg-query -s nginx &>/dev/null && echo "nginx is installed" Nothing should be returned. - OR - - IF - a package is installed and is required for dependencies: - IF - the httpd package is required for dependencies: Run the following command to verify httpd.socket and httpd.service UnitFileState is not enabled and ActiveState is not active: # systemctl show httpd.socket httpd.service -p UnitFileState,ActiveState | grep -Pi '=(enabled|active)' Nothing should be returned - IF - the nginx package is required for dependencies: Run the following command to verify nginx.service UnitFileState is not enabled and ActiveState is not active: # systemctl show nginx.service -p UnitFileState,ActiveState | grep -Pi '=(enabled|active)' Nothing should be returned Note: • Other web server packages may exist. They should also be audited, if not required and authorized by local site policy • If the package is required for a dependency: o Ensure the dependent package is approved by local site policy o Ensure stopping and masking the service and/or socket meets local site policy Page 256 Internal Only - General Remediation: Run the following commands to stop httpd.socket, httpd.service and remove the apache2 package: # systemctl stop apache2.socket apache2.service # apt purge apache2 Run the following commands to stop nginx.service and remove the nginx package: # systemctl stop nginx.service # apt purge nginx - OR - - IF - a package is installed and is required for dependencies: - IF - the httpd package is required for dependencies: Run the following commands to stop and mask httpd.socket and httpd.service: # systemctl stop httpd.socket httpd.service # systemctl mask httpd.socket httpd.service - IF - the nginx package is required for dependencies: Run the following commands to stop and mask nginx.service: # systemctl stop nginx.service # systemctl mask nginx.service Note: Other web server packages may exist. If not required and authorized by local site policy, they should also be removed. If the package is required for a dependency, the service and socket should be stopped and masked. References: 1. NIST SP 800-53 :: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 257 Internal Only - General 2.1.19 Ensure xinetd services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The eXtended InterNET Daemon (xinetd) is an open source super daemon that replaced the original inetd daemon. The xinetd daemon listens for well known services and dispatches the appropriate daemon to properly respond to service requests. Rationale: If there are no xinetd services required, it is recommended that the package be removed to reduce the attack surface are of the system. Note: If an xinetd service or services are required, ensure that any xinetd service not required is stopped and masked Impact: There may be packages that are dependent on the xinetd package. If the xinetd package is removed, these dependent packages will be removed as well. Before removing the xinetd package, review any dependent packages to determine if they are required on the system. -IF- a dependent package is required: stop and mask xinetd.service leaving the xinetd package installed. Page 258 Internal Only - General Audit: Run the following command to verify the xinetd package is not installed: # dpkg-query -s xinetd &>/dev/null && echo "xinetd is installed" Nothing should be returned. -OR- -IF- the xinetd package is required as a dependency: Run the following command to verify xinetd.service is not enabled: # systemctl is-enabled xinetd.service 2>/dev/null | grep 'enabled' Nothing should be returned Run the following command to verify xinetd.service is not active: # systemctl is-active xinetd.service 2>/dev/null | grep '^active' Nothing should be returned Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop xinetd.service, and remove the xinetd package: # systemctl stop xinetd.service # apt purge xinetd -OR- -IF- the xinetd package is required as a dependency: Run the following commands to stop and mask the xinetd.service: # systemctl stop xinetd.service # systemctl mask xinetd.service References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 259 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 260 Internal Only - General 2.1.20 Ensure X window server services are not in use (Automated) Profile Applicability: • Level 2 - Server Description: The X Window System provides a Graphical User Interface (GUI) where users can have multiple windows in which to run programs and various add on. The X Windows system is typically used on workstations where users login, but not on servers where users typically do not login. Rationale: Unless your organization specifically requires graphical login access via X Windows, remove it to reduce the potential attack surface. Impact: If a Graphical Desktop Manager (GDM) is in use on the system, there may be a dependency on the xorg-x11-server-common package. If the GDM is required and approved by local site policy, the package should not be removed. Many Linux systems run applications which require a Java runtime. Some Linux Java packages have a dependency on specific X Windows xorg-x11-fonts. One workaround to avoid this dependency is to use the "headless" Java packages for your specific Java runtime. Audit: - IF - a Graphical Desktop Manager or X-Windows server is not required and approved by local site policy: Run the following command to Verify X Windows Server is not installed. dpkg-query -s xserver-common &>/dev/null && echo "xserver-common is installed" Nothing should be returned Remediation: - IF - a Graphical Desktop Manager or X-Windows server is not required and approved by local site policy: Run the following command to remove the X Windows Server package: # apt purge xserver-common References: 1. NIST SP 800-53 Rev. 5: CM-11 Page 261 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 2.6 Address unapproved software v7 Ensure that unauthorized software is either removed or the inventory is ● ● ● updated in a timely manner Page 262 Internal Only - General 2.1.21 Ensure mail transfer agents are configured for local-only mode (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Mail Transfer Agents (MTA), such as sendmail and Postfix, are used to listen for incoming mail and transfer the messages to the appropriate user or mail server. If the system is not intended to be a mail server, it is recommended that the MTA be configured to only process local mail. Rationale: The software for all Mail Transfer Agents is complex and most have a long history of security issues. While it is important to ensure that the system can process local mail messages, it is not necessary to have the MTA's daemon listening on a port unless the server is intended to be a mail server that receives and processes mail from other systems. Impact: This recommendation is designed around the postfix mail server. Depending on your environment you may have an alternative MTA installed such as exim4 or sendmail. If this is the case consult the documentation for your installed MTA to configure the recommended state. Page 263 Internal Only - General Audit: Run the following script to verify that the MTA is not listening on any non-loopback address ( 127.0.0.1 or ::1 ) #!/usr/bin/env bash { a_output=(); a_output2=(); a_port_list=("25" "465" "587") for l_port_number in "${a_port_list[@]}"; do if ss -plntu | grep -P -- ':'"$l_port_number"'\b' | grep -Pvq -- '\h+(127\.0\.0\.1|\[?::1\]?):'"$l_port_number"'\b'; then a_output2+=(" - Port \"$l_port_number\" is listening on a non- loopback network interface") else a_output+=(" - Port \"$l_port_number\" is not listening on a non- loopback network interface") fi done if command -v postconf &> /dev/null; then l_interfaces="$(postconf -n inet_interfaces)" elif command -v exim &> /dev/null; then l_interfaces="$(exim -bP local_interfaces)" elif command -v sendmail &> /dev/null; then l_interfaces="$(grep -i "O DaemonPortOptions=" /etc/mail/sendmail.cf | grep -oP '(?<=Addr=)[^,+]+' | grep -v '^127\.0\.0\.1$')" fi if [ -n "$l_interfaces" ]; then if grep -Pqi '\ball\b' <<< "$l_interfaces"; then a_output2+=(" - MTA is bound to all network interfaces") elif ! grep -Pqi '(inet_interfaces\h*=\h*)?(0\.0\.0\.0|::1|loopback- only)' <<< "$l_interfaces"; then a_output2+=(" - MTA is bound to a network interface" " \"$l_interfaces\"") else a_output+=(" - MTA is not bound to a non loopback network interface" " \"$l_interfaces\"") fi else a_output+=(" - MTA not detected or in use") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 264 Internal Only - General Remediation: Edit /etc/postfix/main.cf and add the following line to the RECEIVING MAIL section. If the line already exists, change it to look like the line below: inet_interfaces = loopback-only Run the following command to restart postfix: # systemctl restart postfix Note: • This recommendation is designed around the postfix mail server. • Depending on your environment you may have an alternative MTA installed such as exim4 or sendmail. If this is the case consult the documentation for your installed MTA to configure the recommended state. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 265 Internal Only - General 2.1.22 Ensure only approved services are listening on a network interface (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A network port is identified by its number, the associated IP address, and the type of the communication protocol such as TCP or UDP. A listening port is a network port on which an application or process listens on, acting as a communication endpoint. Each listening port can be open or closed (filtered) using a firewall. In general terms, an open port is a network port that accepts incoming packets from remote locations. Rationale: Services listening on the system pose a potential risk as an attack vector. These services should be reviewed, and if not required, the service should be stopped, and the package containing the service should be removed. If required packages have a dependency, the service should be stopped and masked to reduce the attack surface of the system. Impact: There may be packages that are dependent on the service's package. If the service's package is removed, these dependent packages will be removed as well. Before removing the service's package, review any dependent packages to determine if they are required on the system. - IF - a dependent package is required: stop and mask the .socket and .service leaving the service's package installed. Audit: Run the following command: # ss -plntu Review the output to ensure: • All services listed are required on the system and approved by local site policy. • Both the port and interface the service is listening on are approved by local site policy. • If a listed service is not required: o Remove the package containing the service o - IF - the service's package is required for a dependency, stop and mask the service and/or socket Page 266 Internal Only - General Remediation: Run the following commands to stop the service and remove the package containing the service: # systemctl stop .socket .service # apt purge - OR - If required packages have a dependency: Run the following commands to stop and mask the service and socket: # systemctl stop .socket .service # systemctl mask .socket .service Note: replace with the appropriate service name. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 267 Internal Only - General 2.2 Configure Client Services A number of insecure services exist. While disabling the servers prevents a local attack against these services, it is advised to remove their clients unless they are required. Note: This should not be considered a comprehensive list of insecure service clients. You may wish to consider additions to those listed here for your environment. Page 268 Internal Only - General 2.2.1 Ensure nis client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Network Information Service (NIS), formerly known as Yellow Pages, is a client- server directory service protocol used to distribute system configuration files. The NIS client was used to bind a machine to an NIS server and receive the distributed configuration files. Rationale: The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that the service be removed. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify nis is not installed. Use the following command to provide the needed information: # dpkg-query -s nis &>/dev/null && echo "nis is installed" Nothing should be returned. Remediation: Uninstall nis: # apt purge nis References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 Page 269 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 2.6 Address unapproved software v7 Ensure that unauthorized software is either removed or the inventory is ● ● ● updated in a timely manner Page 270 Internal Only - General 2.2.2 Ensure rsh client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsh-client package contains the client commands for the rsh services. Rationale: These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inadvertently attempting to use these commands and therefore exposing their credentials. Note that removing the rsh- client package removes the clients for rsh , rcp and rlogin . Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify rsh-client is not installed. Use the following command to provide the needed information: # dpkg-query -s rsh-client &>/dev/null && echo "rsh-client is installed" Nothing should be returned. Remediation: Uninstall rsh: # apt purge rsh-client References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 271 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 272 Internal Only - General 2.2.3 Ensure talk client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The talk software makes it possible for users to send and receive messages across systems through a terminal session. The talk client, which allows initialization of talk sessions, is installed by default. Rationale: The software presents a security risk as it uses unencrypted protocols for communication. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify talk is not installed. The following command may provide the needed information: # dpkg-query -s talk &>/dev/null && echo "talk is installed" Nothing should be returned. Remediation: Uninstall talk: # apt purge talk References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 273 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 274 Internal Only - General 2.2.4 Ensure telnet client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The telnet package contains the telnet client, which allows users to start connections to other systems via the telnet protocol. Rationale: The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in most Linux distributions. Impact: Many insecure service clients are used as troubleshooting tools and in testing environments. Uninstalling them can inhibit capability to test and troubleshoot. If they are required it is advisable to remove the clients after use to prevent accidental or intentional misuse. Audit: Verify telnet is not installed. Use the following command to provide the needed information: # dpkg-query -s telnet &>/dev/null && echo "telnet is installed" Nothing should be returned. Remediation: Uninstall telnet: # apt purge telnet References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 Page 275 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 276 Internal Only - General 2.2.5 Ensure ldap client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Lightweight Directory Access Protocol (LDAP) was introduced as a replacement for NIS/YP. It is a service that provides a method for looking up information from a central database. Rationale: If the system will not need to act as an LDAP client, it is recommended that the software be removed to reduce the potential attack surface. Impact: Removing the LDAP client will prevent or inhibit using LDAP for authentication in your environment. Audit: Verify that ldap-utils is not installed. Use the following command to provide the needed information: # dpkg-query -s ldap-utils &>/dev/null && echo "ldap-utils is installed" Nothing should be returned. Remediation: Uninstall ldap-utils: # apt purge ldap-utils References: 1. NIST SP 800-53 Rev. 5: CM-7 Page 277 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 278 Internal Only - General 2.2.6 Ensure ftp client is not installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: tnftp an enhanced FTP client, is the user interface to the Internet standard File Transfer Protocol. The program allows a user to transfer files to and from a remote network site. Rationale: Unless there is a need to run the system using Internet standard File Transfer Protocol (for example, to allow anonymous downloads), it is recommended that the package be removed to reduce the potential attack surface. Audit: Verify tnftp & ftp is not installed. Use the following command to provide the needed information: # dpkg-query -l | awk '{print $2}' | grep -E '^ftp|^tnftp' &>/dev/null && echo "ftp is installed" Nothing should be returned. Remediation: Run the following commands to uninstall tnftp & ftp: # apt purge ftp # apt purge tnftp References: 1. NIST SP 800-53 Rev. 5: CM-7, CM-11 Page 279 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 280 Internal Only - General 2.3 Configure Time Synchronization It is recommended that systems be configured to synchronize their time using a service such as systemd-timesyncd, or chrony. Virtual systems may be configured to receive their time synchronization from their host system. The host system must be configured to synchronize its time from an authoritative source to be considered compliant with this section. Any "physical" clock present on a system should be synchronized from an authoritative time source. Only one time synchronization method should be in use on the system Notes: Only the section related to the time synchronization method in use on the system should be followed, all other time synchronization recommendations should be skipped Page 281 Internal Only - General 2.3.1 Ensure time synchronization is in use It is recommended that physical systems and virtual guests lacking direct access to the physical host's clock be configured to synchronize their time using a service such as systemd-timesyncd, or chrony. Page 282 Internal Only - General 2.3.1.1 Ensure a single time synchronization daemon is in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize their clocks to them. Note: • On virtual systems where host based time synchronization is available consult your virtualization software documentation and verify that host based synchronization is in use and follows local site policy. In this scenario, this section should be skipped • Only one time synchronization method should be in use on the system. Configuring multiple time synchronization methods could lead to unexpected or unreliable results Rationale: Time synchronization is important to support time sensitive security mechanisms and ensures log files have consistent time records across the enterprise, which aids in forensic investigations. Audit: On physical systems, and virtual systems where host based time synchronization is not available. One of the two time synchronization daemons should be available; chrony or systemd- timesyncd Run the following script to verify that a single time synchronization daemon is available on the system: Page 283 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" service_not_enabled_chk() { l_out2="" if systemctl is-enabled "$l_service_name" 2>/dev/null | grep -q 'enabled'; then l_out2="$l_out2\n - Daemon: \"$l_service_name\" is enabled on the system" fi if systemctl is-active "$l_service_name" 2>/dev/null | grep -q '^active'; then l_out2="$l_out2\n - Daemon: \"$l_service_name\" is active on the system" fi } l_service_name="systemd-timesyncd.service" # Check systemd-timesyncd daemon service_not_enabled_chk if [ -n "$l_out2" ]; then l_timesyncd="y" l_out_tsd="$l_out2" else l_timesyncd="n" l_out_tsd="\n - Daemon: \"$l_service_name\" is not enabled and not active on the system" fi l_service_name="chrony.service" # Check chrony service_not_enabled_chk if [ -n "$l_out2" ]; then l_chrony="y" l_out_chrony="$l_out2" else l_chrony="n" l_out_chrony="\n - Daemon: \"$l_service_name\" is not enabled and not active on the system" fi l_status="$l_timesyncd$l_chrony" case "$l_status" in yy) l_output2=" - More than one time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; nn) l_output2=" - No time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; yn|ny) l_output=" - Only one time sync daemon is in use on the system$l_out_tsd$l_out_chrony" ;; *) l_output2=" - Unable to determine time sync daemon(s) status" ;; esac if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :\n$l_output2\n" fi } Page 284 Internal Only - General Note: Follow the guidance in the subsection for the time synchronization daemon available on the system and skip the other time synchronization daemon subsection. Remediation: On physical systems, and virtual systems where host based time synchronization is not available. Select one of the two time synchronization daemons; chrony (1) or systemd- timesyncd (2) and following the remediation procedure for the selected daemon. Note: enabling more than one synchronization daemon could lead to unexpected or unreliable results: 1. chrony Run the following command to install chrony: # apt install chrony Run the following commands to stop and mask the systemd-timesyncd daemon: # systemctl stop systemd-timesyncd.service # systemctl mask systemd-timesyncd.service Note: • Subsection: Configure chrony should be followed • Subsection: Configure systemd-timesyncd should be skipped 2. systemd-timesyncd Run the following command to remove the chrony package: # apt purge chrony # apt autoremove chrony Note: • Subsection: Configure systemd-timesyncd should be followed • Subsection: Configure chrony should be skipped References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-12 Page 285 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 286 Internal Only - General 2.3.2 Configure systemd-timesyncd systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network. It implements an SNTP client. In contrast to NTP implementations such as chrony or the NTP reference server this only implements a client side, and does not bother with the full NTP complexity, focusing only on querying time from one remote server and synchronizing the local clock to it. The daemon runs with minimal privileges, and has been hooked up with networkd to only operate when network connectivity is available. The daemon saves the current clock to disk every time a new NTP sync has been acquired, and uses this to possibly correct the system clock early at bootup, in order to accommodate for systems that lack an RTC such as the Raspberry Pi and embedded devices, and make sure that time monotonically progresses on these systems, even if it is not always correct. To make use of this daemon a new system user and group "systemd-timesync" needs to be created on installation of systemd. The default configuration is set during compilation, so configuration is only needed when it is necessary to deviate from those defaults. Initially, the main configuration file in /etc/systemd/ contains commented out entries showing the defaults as a guide to the administrator. Local overrides can be created by editing this file or by creating drop-ins, as described below. Using drop-ins for local configuration is recommended over modifications to the main configuration file. In addition to the "main" configuration file, drop-in configuration snippets are read from /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those drop-ins have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. When packages need to customize the configuration, they can install drop-ins under /usr/. Files in /etc/ are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages. Drop-ins have to be used to override package drop-ins, since the main configuration file has lower precedence. It is recommended to prefix all filenames in those subdirectories with a two-digit number and a dash, to simplify the ordering of the files. To disable a configuration file supplied by the vendor, the recommended way is to place a symlink to /dev/null in the configuration directory in /etc/, with the same filename as the vendor configuration file. Note: • The recommendations in this section only apply if timesyncd is in use on the system • The systemd-timesyncd service specifically implements only SNTP. o This minimalistic service will set the system clock for large offsets or slowly adjust it for smaller deltas Page 287 Internal Only - General o More complex use cases are not covered by systemd-timesyncd • If chrony is used, systemd-timesyncd should be stopped and masked, and this section skipped • One, and only one, time synchronization method should be in use on the system Page 288 Internal Only - General 2.3.2.1 Ensure systemd-timesyncd configured with authorized timeserver (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: NTP= • A space-separated list of NTP server host names or IP addresses. During runtime this list is combined with any per-interface NTP servers acquired from systemd-networkd.service(8). systemd-timesyncd will contact all configured system or per-interface servers in turn, until one responds. When the empty string is assigned, the list of NTP servers is reset, and all prior assignments will have no effect. This setting defaults to an empty list. FallbackNTP= • A space-separated list of NTP server host names or IP addresses to be used as the fallback NTP servers. Any per-interface NTP servers obtained from systemd- networkd.service(8) take precedence over this setting, as do any servers set via NTP= above. This setting is hence only relevant if no other NTP server information is known. When the empty string is assigned, the list of NTP servers is reset, and all prior assignments will have no effect. If this option is not given, a compiled-in list of NTP servers is used. Rationale: Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: Run the following command to verify the NTP and/or FallbackNTP option is set to local site approved authoritative time server(s): Page 289 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_output3=() a_out=() a_out2=() a_parlist=("NTP=[^#\n\r]+" "FallbackNTP=[^#\n\r]+") l_analyze_cmd="$(readlink -f /bin/systemd-analyze)" l_systemd_config_file="/etc/systemd/timesyncd.conf" f_config_file_parameter_chk() { l_used_parameter_setting="" while IFS= read -r l_file; do l_file="$(tr -d '# ' <<< "$l_file")" l_used_parameter_setting="$(grep -PHs -- '^\h*'"$l_parameter_name"'\b' "$l_file" | tail -n 1)" [ -n "$l_used_parameter_setting" ] && break done < <($l_analyze_cmd cat-config "$l_systemd_config_file" | tac | grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ -n "$l_used_parameter_setting" ]; then while IFS=: read -r l_file_name l_file_parameter; do while IFS="=" read -r l_file_parameter_name l_file_parameter_value; do if grep -Pq -- "$l_parameter_value" <<< "$l_file_parameter_value"; then a_out+=(" - Parameter: \"${l_file_parameter_name// /}\"" \ " correctly set to: \"${l_file_parameter_value// /}\"" \ " in the file: \"$l_file_name\"") else a_out2+=(" - Parameter: \"${l_file_parameter_name// /}\"" \ " incorrectly set to: \"${l_file_parameter_value// /}\"" \ " in the file: \"$l_file_name\"" \ " Should be set to: \"$l_value_out\"") fi done <<< "$l_file_parameter" done <<< "$l_used_parameter_setting" else a_out2+=(" - Parameter: \"$l_parameter_name\" is not set in an included file" \ " *** Note: \"$l_parameter_name\" May be set in a file that's ignored by load procedure ***") fi } while IFS="=" read -r l_parameter_name l_parameter_value; do # Assess and check parameters l_parameter_name="${l_parameter_name// /}"; l_parameter_value="${l_parameter_value// /}" l_value_out="${l_parameter_value//-/ through }"; l_value_out="${l_value_out//|/ or }" l_value_out="$(tr -d '(){}' <<< "$l_value_out")" f_config_file_parameter_chk done < <(printf '%s\n' "${a_parlist[@]}") if [ "${#a_out[@]}" -gt 0 ]; then a_output+=("${a_out[@]}"); [ "${#a_out2[@]}" -gt 0 ] && a_output3+=(" ** INFO: **" "${a_out2[@]}") else a_output2+=("${a_out2[@]}") fi if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "${a_output3[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } Note: Please ensure the output for NTP and/or FallbackNTP is in accordance with local site policy. The timeservers in the example output are provided as an example of possible timeservers and they may not follow local site policy. Page 290 Internal Only - General Remediation: Set NTP and/or FallbackNTP parameters to local site approved authoritative time server(s) in /etc/systemd/timesyncd.conf or a file in /etc/systemd/timesyncd.conf.d/ ending in .conf in the [Time] section: Example file: [Time] NTP=time.nist.gov # Uses the generic name for NIST's time servers FallbackNTP=time-a-g.nist.gov time-b-g.nist.gov time-c-g.nist.gov # Space separated list of NIST time servers Example script to create systemd drop-in configuration file: #!/usr/bin/env bash { a_settings=("NTP=time.nist.gov" "FallbackNTP=time-a-g.nist.gov time-b- g.nist.gov time-c-g.nist.gov") [ ! -d /etc/systemd/timesyncd.conf.d/ ] && mkdir /etc/systemd/timesyncd.conf.d/ if grep -Psq -- '^\h*\[Time\]' /etc/systemd/timesyncd.conf.d/60- timesyncd.conf; then printf '%s\n' "" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf else printf '%s\n' "" "[Time]" "${a_settings[@]}" >> /etc/systemd/timesyncd.conf.d/60-timesyncd.conf fi } Note: If this setting appears in a canonically later file, or later in the same file, the setting will be overwritten Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-timesyncd Default Value: #NTP= #FallbackNTP= References: 1. https://www.freedesktop.org/software/systemd/man/timesyncd.conf.html 2. https://tf.nist.gov/tf-cgi/servers.cgi 3. NIST SP 800-53 Rev. 5: AU-7, AU-8 Page 291 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 292 Internal Only - General 2.3.2.2 Ensure systemd-timesyncd is enabled and running (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: systemd-timesyncd is a daemon that has been added for synchronizing the system clock across the network Rationale: systemd-timesyncd needs to be enabled and running in order to synchronize the system to a timeserver. Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: - IF - systemd-timesyncd is in use on the system, run the following commands: Run the following command to verify that the systemd-timesyncd service is enabled: # systemctl is-enabled systemd-timesyncd.service enabled Run the following command to verify that the systemd-timesyncd service is active: # systemctl is-active systemd-timesyncd.service active Remediation: - IF - systemd-timesyncd is in use on the system, run the following commands: Run the following command to unmask systemd-timesyncd.service: # systemctl unmask systemd-timesyncd.service Run the following command to enable and start systemd-timesyncd.service: # systemctl --now enable systemd-timesyncd.service - OR - If another time synchronization service is in use on the system, run the following command to stop and mask systemd-timesyncd: # systemctl --now mask systemd-timesyncd.service Page 293 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-7, AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 294 Internal Only - General 2.3.3 Configure chrony chrony is a daemon which implements the Network Time Protocol (NTP) and is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. chrony can be configured to be a client and/or a server. More information on chrony can be found at: http://chrony.tuxfamily.org/. Note: • If systemd-timesyncd is being used, chrony should be removed and this section skipped • Only one time synchronization method should be in use on the system Page 295 Internal Only - General 2.3.3.1 Ensure chrony is configured with authorized timeserver (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: • server o The server directive specifies an NTP server which can be used as a time source. The client-server relationship is strictly hierarchical: a client might synchronize its system time to that of the server, but the server’s system time will never be influenced by that of a client. o This directive can be used multiple times to specify multiple servers. o The directive is immediately followed by either the name of the server, or its IP address. • pool o The syntax of this directive is similar to that for the server directive, except that it is used to specify a pool of NTP servers rather than a single NTP server. The pool name is expected to resolve to multiple addresses which might change over time. o This directive can be used multiple times to specify multiple pools. o All options valid in the server directive can be used in this directive too. Rationale: Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Page 296 Internal Only - General Audit: - IF - chrony is in use on the system, run the following script to ensure chrony is configured with an authorized timeserver: #!/usr/bin/env bash { a_output=() a_output2=() a_config_files=("/etc/chrony/chrony.conf") l_include='(confdir|sourcedir)' l_parameter_name='(server|pool)' l_parameter_value='.+' while IFS= read -r l_conf_loc; do l_dir="" l_ext="" if [ -d "$l_conf_loc" ]; then l_dir="$l_conf_loc" l_ext="*" elif grep -Psq '\/\*\.([^#/\n\r]+)?\h*$' <<< "$l_conf_loc" || [ -f "$(readlink -f "$l_conf_loc")" ]; then l_dir="$(dirname "$l_conf_loc")" l_ext="$(basename "$l_conf_loc")" fi if [[ -n "$l_dir" && -n "$l_ext" ]]; then while IFS= read -r -d $'\0' l_file_name; do [ -f "$(readlink -f "$l_file_name")" ] && a_config_files+=("$(readlink -f "$l_file_name")") done < <(find -L "$l_dir" -type f -name "$l_ext" -print0 2>/dev/null) fi done < <(awk '$1~/^\s*'"$l_include"'$/{print $2}' "${a_config_files[*]}" 2>/dev/null) for l_file in "${a_config_files[@]}"; do l_parameter_line="$(grep -Psi '^\h*'"$l_parameter_name"'(\h+|\h*:\h*)'"$l_parameter_value"'\b' "$l_file")" [ -n "$l_parameter_line" ] && a_output+=(" - Parameter: \"$(tr -d '()' <<< ${l_parameter_name//|/ or })\"" \ " Exists in the file: \"$l_file\" as:" "$l_parameter_line") done [ "${#a_output[@]}" -le "0" ] && a_output2+=(" - Parameter: \"$(tr -d '()' <<< ${l_parameter_name//|/ or })\"" \ " Does not exist in the chrony configuration") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" fi } Page 297 Internal Only - General Remediation: Edit /etc/chrony/chrony.conf or a file ending in .sources in /etc/chrony/sources.d/ and add or edit server or pool lines as appropriate according to local site policy: Edit the Chrony configuration and add or edit the server and/or pool lines returned by the Audit Procedure as appropriate according to local site policy <[server|pool]> <[remote-server|remote-pool]> Example script to add a drop-in configuration for the pool directive: #!/usr/bin/env bash { [ ! -d "/etc/chrony/sources.d/" ] && mkdir /etc/chrony/sources.d/ printf '%s\n' "" "#The maxsources option is unique to the pool directive" \ "pool time.nist.gov iburst maxsources 4" >> /etc/chrony/sources.d/60- sources.sources chronyc reload sources &>/dev/null } Example script to add a drop-in configuration for the server directive: #!/usr/bin/env bash { [ ! -d "/etc/chrony/sources.d/" ] && mkdir /etc/chrony/sources.d/ printf '%s\n' "" "server time-a-g.nist.gov iburst" "server 132.163.97.3 iburst" \ "server time-d-b.nist.gov iburst" >> /etc/chrony/sources.d/60- sources.sources chronyc reload sources &>/dev/null } Run the following command to reload the chronyd config: # systemctl reload-or-restart chronyd References: 1. chrony.conf(5) Manual Page 2. https://tf.nist.gov/tf-cgi/servers.cgi 3. NIST SP 800-53 Rev. 5: AU-3, AU-12 Additional Information: If pool and/or server directive(s) are set in a sources file in /etc/chrony/sources.d, the line: sourcedir /etc/chrony/sources.d must be present in /etc/chrony/chrony.conf Page 298 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 299 Internal Only - General 2.3.3.2 Ensure chrony is running as user _chrony (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The chrony package is installed with a dedicated user account _chrony. This account is granted the access required by the chronyd service Rationale: The chronyd service should run with only the required privlidges Audit: - IF - chrony is in use on the system, run the following command to verify the chronyd service is being run as the _chrony user: # ps -ef | awk '(/[c]hronyd/ && $1!="_chrony") { print $1 }' Nothing should be returned Remediation: Add or edit the user line to /etc/chrony/chrony.conf or a file ending in .conf in /etc/chrony/conf.d/: user _chrony - OR - If another time synchronization service is in use on the system, run the following command to remove chrony from the system: # apt purge chrony # apt autoremove chrony Default Value: user _chrony References: 1. NIST SP 800-53 Rev. 5: AU-8 Page 300 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 301 Internal Only - General 2.3.3.3 Ensure chrony is enabled and running (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: chrony is a daemon for synchronizing the system clock across the network Rationale: chrony needs to be enabled and running in order to synchronize the system to a timeserver. Time synchronization is important to support time sensitive security mechanisms and to ensure log files have consistent time records across the enterprise to aid in forensic investigations Audit: - IF - chrony is in use on the system, run the following commands: Run the following command to verify that the chrony service is enabled: # systemctl is-enabled chrony.service enabled Run the following command to verify that the chrony service is active: # systemctl is-active chrony.service active Remediation: - IF - chrony is in use on the system, run the following commands: Run the following command to unmask chrony.service: # systemctl unmask chrony.service Run the following command to enable and start chrony.service: # systemctl --now enable chrony.service - OR - If another time synchronization service is in use on the system, run the following command to remove chrony: # apt purge chrony # apt autoremove chrony References: 1. NIST SP 800-53 Rev. 5: AU-8 Page 302 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.4 Standardize Time Synchronization v8 Standardize time synchronization. Configure at least two synchronized time ● ● sources across enterprise assets, where supported. 6.1 Utilize Three Synchronized Time Sources v7 Use at least three synchronized time sources from which all servers and network devices retrieve time information on a regular basis so that timestamps ● ● in logs are consistent. Page 303 Internal Only - General 2.4 Job Schedulers A job scheduler is used to execute jobs, commands, or shell scripts, at fixed times, dates, or intervals Page 304 Internal Only - General 2.4.1 Configure cron cron is a time based job scheduler - IF - cron is not installed on the system, this sub section can be skipped Note: Other methods such as systemd timers exist for scheduling jobs. If an alternate method is in use, it should be secured in accordance with local site policy Page 305 Internal Only - General 2.4.1.1 Ensure cron daemon is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The cron daemon is used to execute batch jobs on the system. Rationale: While there may not be user jobs that need to be run on the system, the system does have maintenance jobs that may include security monitoring that have to run, and cron is used to execute them. Audit: - IF - cron is installed on the system: Run the following command to verify cron is enabled: # systemctl list-unit-files | awk '$1~/^crond?\.service/{print $2}' enabled Run the following command to verify that cron is active: # systemctl list-units | awk '$1~/^crond?\.service/{print $3}' active Remediation: - IF - cron is installed on the system: Run the following commands to unmask, enable, and start cron: # systemctl unmask "$(systemctl list-unit-files | awk '$1~/^crond?\.service/{print $1}')" # systemctl --now enable "$(systemctl list-unit-files | awk '$1~/^crond?\.service/{print $1}')" References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 306 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 307 Internal Only - General 2.4.1.2 Ensure access to /etc/crontab is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/crontab file is used by cron to control its own jobs. The commands in this item make sure that root is the user and group owner of the file and that only the owner can access the file. Rationale: This file contains information on what system jobs are run by cron. Write access to these files could provide unprivileged users with the ability to elevate their privileges. Read access to these files could provide users with the ability to gain insight on system jobs that run on the system and could provide them a way to gain unauthorized privileged access. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other : # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/crontab Access: (600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on /etc/crontab: # chown root:root /etc/crontab # chmod og-rwx /etc/crontab Default Value: Access: (644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 308 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 309 Internal Only - General 2.4.1.3 Ensure access to /etc/cron.hourly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: This directory contains system cron jobs that need to run on an hourly basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.hourly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.hourly directory: # chown root:root /etc/cron.hourly/ # chmod og-rwx /etc/cron.hourly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 310 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 311 Internal Only - General 2.4.1.4 Ensure access to /etc/cron.daily is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.daily directory contains system cron jobs that need to run on a daily basis. The files in this directory cannot be manipulated by the crontab command, but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.daily/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.daily directory: # chown root:root /etc/cron.daily/ # chmod og-rwx /etc/cron.daily/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 312 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 313 Internal Only - General 2.4.1.5 Ensure access to /etc/cron.weekly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.weekly directory contains system cron jobs that need to run on a weekly basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.weekly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.weekly directory: # chown root:root /etc/cron.weekly/ # chmod og-rwx /etc/cron.weekly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 314 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 315 Internal Only - General 2.4.1.6 Ensure access to /etc/cron.monthly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.monthly directory contains system cron jobs that need to run on a monthly basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.monthly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.monthly directory: # chown root:root /etc/cron.monthly/ # chmod og-rwx /etc/cron.monthly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 316 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 317 Internal Only - General 2.4.1.7 Ensure access to /etc/cron.yearly is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.yearly directory contains system cron jobs that need to run on an annual basis. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.yearly/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.yearly directory: # chown root:root /etc/cron.yearly/ # chmod og-rwx /etc/cron.yearly/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 318 Internal Only - General 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/cron.d directory contains system cron jobs that need to run in a similar manner to the hourly, daily weekly and monthly jobs from /etc/crontab, but require more granular control as to when they run. The files in this directory cannot be manipulated by the crontab command but are instead edited by system administrators using a text editor. The commands below restrict read/write and search access to user and group root, preventing regular users from accessing this directory. Rationale: Granting write access to this directory for non-privileged users could provide them the means for gaining unauthorized elevated privileges. Granting read access to this directory could give an unprivileged user insight in how to gain elevated privileges or circumvent auditing controls. Audit: - IF - cron is installed on the system: Run the following command and verify Uid and Gid are both 0/root and Access does not grant permissions to group or other: # stat -Lc 'Access: (%a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/cron.d/ Access: (700/drwx------) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: - IF - cron is installed on the system: Run the following commands to set ownership and permissions on the /etc/cron.d directory: # chown root:root /etc/cron.d/ # chmod og-rwx /etc/cron.d/ Default Value: Access: (755/drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 319 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 320 Internal Only - General 2.4.1.9 Ensure access to crontab is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: crontab is the program used to install, deinstall, or list the tables used to drive the cron daemon. Each user can have their own crontab, and though files are created, they are not intended to be edited directly. If the /etc/cron.allow file exists, then you must be listed (one user per line) therein in order to be allowed to use this command. If the /etc/cron.allow file does not exist but the /etc/cron.deny file does exist, then you must not be listed in the /etc/cron.deny file in order to use this command. If neither of these files exists, then depending on site-dependent configuration parameters, only the super user will be allowed to use this command, or all users will be able to use this command. If both files exist then /etc/cron.allow takes precedence. Which means that /etc/cron.deny is not considered and your user must be listed in /etc/cron.allow in order to be able to use the crontab. Regardless of the existence of any of these files, the root administrative user is always allowed to setup a crontab. The files /etc/cron.allow and /etc/cron.deny, if they exist, must be either world- readable, or readable by group crontab. If they are not, then cron will deny access to all users until the permissions are fixed. There is one file for each user's crontab. Users are not allowed to edit the file directly to ensure that only users allowed by the system to run periodic tasks can add them, and only syntactically correct crontabs will be written. This is enforced by having the directory writable only by the crontab group and configuring crontab command with the setgid bid set for that specific group. Note: • The files /etc/cron.allow and /etc/cron.deny, if they exist, only controls administrative access to the crontab command for scheduling and modifying cron jobs • If you are using SELinux or AppArmor, these security modules may prevent crontab access. Check the audit logs for any related permission denied entries and adjust your policies if necessary. Page 321 Internal Only - General Rationale: On many systems, only the system administrator is authorized to schedule cron jobs. Using the cron.allow file to control who can run cron jobs enforces this policy. It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user ID to the system and forget to add it to the deny files. Impact: When the /etc/cron.allow file exists, a user must be listed, one user per line, in the /etc/cron.allow file in order to be allowed to use the crontab command. Audit: - IF - cron is installed on the system: Run the following command to verify /etc/cron.allow: • Exists • Is mode 0640 or more restrictive • Is owned by the user root • Is group owned by the group root - OR - the group crontab # stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/cron.allow Verify the returned value is: Access: (640/-rw-r-----) Owner: (root) Group: (root) - OR - Access: (640/-rw-r-----) Owner: (root) Group: (crontab) Run the following command to verify either cron.deny doesn't exist or is: • Mode 0640 or more restrictive • Owned by the user root • Is group owned by the group root - OR - the group crontab # [ -e "/etc/cron.deny" ] && stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/cron.deny Verify either nothing is returned - OR - returned value is one of the following: Access: (640/-rw-r-----) Owner: (root) Group: (root) - OR - Access: (640/-rw-r-----) Owner: (root) Group: (crontab) Note: On systems where cron is configured to use the group crontab, if the group crontab is not set as the owner of cron.allow, then cron will deny access to all users and you will see an error similar to: You () are not allowed to use this program (crontab) See crontab(1) for more information Page 322 Internal Only - General Remediation: - IF - cron is installed on the system: Run the following script to: • Create /etc/cron.allow if it doesn't exist • Change owner to user root • Change group owner to group root - OR - group crontab if it exists • Change mode to 640 or more restrictive #!/usr/bin/env bash { [ ! -e "/etc/cron.allow" ] && touch /etc/cron.allow chmod u-x,g-wx,o-rwx /etc/cron.allow if grep -Pq -- '^\h*crontab\:' /etc/group; then chown root:crontab /etc/cron.allow else chown root:root /etc/cron.allow fi } - IF - /etc/cron.deny exists, run the following script to: • Change owner to user root • Change group owner to group root - OR - group crontab if it exists • Change mode to 640 or more restrictive #!/usr/bin/env bash { if [ -e "/etc/cron.deny" ]; then chmod u-x,g-wx,o-rwx /etc/cron.deny if grep -Pq -- '^\h*crontab\:' /etc/group; then chown root:crontab /etc/cron.deny else chown root:root /etc/cron.deny fi fi } Page 323 Internal Only - General Note: • When the /etc/cron.allow file exists, a user must be listed, one user per line, in the /etc/cron.allow file in order to be allowed to use the crontab command. • If both /etc/cron.allow and /etc/cron.deny exist, /etc/cron.allow takes precedence. Which means that /etc/cron.deny is not considered and users must be listed in /etc/cron.allow in order to use the crontab. • If the /etc/cron.allow file does not exist but the /etc/cron.deny file does exist, then you must not be listed in the /etc/cron.deny file in order to use the crontab command. • Regardless of the existence of any of these files, the root administrative user is always allowed to setup a crontab. • On systems where cron is configured to use the group crontab, if the group crontab is not set as the owner of /etc/cron.allow, then cron will deny access to all users but root, and you will see an error similar to: You () are not allowed to use this program (crontab) See crontab(1) for more information References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 324 Internal Only - General 2.4.2 Configure at at is a command-line utility used to schedule a job for later execution Note: if at is not installed on the system, this section can be skipped Page 325 Internal Only - General 2.4.2.1 Ensure access to at is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: at allows fairly complex time specifications, extending the POSIX.2 standard. It accepts times of the form HH:MM to run a job at a specific time of day. (If that time is already past, the next day is assumed.) You may also specify midnight, noon, or teatime (4pm) and you can have a time-of-day suffixed with AM or PM for running in the morning or the evening. You can also say what day the job will be run, by giving a date in the form month-name day with an optional year, or giving a date of the form MMDD[CC]YY, MM/DD/[CC]YY, DD.MM.[CC]YY or [CC]YY-MM-DD. The specification of a date must follow the specification of the time of day. You can also give times like now + count time-units, where the time-units can be minutes, hours, days, or weeks and you can tell at to run the job today by suffixing the time with today and to run the job tomorrow by suffixing the time with tomorrow. The /etc/at.allow and /etc/at.deny files determine which user can submit commands for later execution via at or batch. The format of the files is a list of usernames, one on each line. Whitespace is not permitted. If the file /etc/at.allow exists, only usernames mentioned in it are allowed to use at. If /etc/at.allow does not exist, /etc/at.deny is checked, every username not mentioned in it is then allowed to use at. An empty /etc/at.deny means that every user may use at. If neither file exists, only the superuser is allowed to use at. Rationale: On many systems, only the system administrator is authorized to schedule at jobs. Using the at.allow file to control who can run at jobs enforces this policy. It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user ID to the system and forget to add it to the deny files. Page 326 Internal Only - General Audit: - IF - at is installed on the system: Run the following command to verify /etc/at.allow: • Exists • Is mode 0640 or more restrictive • Is owned by the user root • Is group owned by the group daemon or group root # stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/at.allow Access: (640/-rw-r-----) Owner: (root) Group: (daemon) -OR- Access: (640/-rw-r-----) Owner: (root) Group: (root) Verify mode is 640 or more restrictive, owner is root, and group is daemon or root Run the following command to verify at.deny doesn't exist, -OR- is: • Mode 0640 or more restrictive • Owned by the user root • Group owned by the group daemon or group root # [ -e "/etc/at.deny" ] && stat -Lc 'Access: (%a/%A) Owner: (%U) Group: (%G)' /etc/at.deny Access: (640/-rw-r-----) Owner: (root) Group: (daemon) -OR- Access: (640/-rw-r-----) Owner: (root) Group: (root) -OR- Nothing is returned If a value is returned, verify mode is 640 or more restrictive, owner is root, and group is daemon or root Page 327 Internal Only - General Remediation: - IF - at is installed on the system: Run the following script to: • /etc/at.allow: o Create the file if it doesn't exist o Change owner or user root o If group daemon exists, change to group daemon, else change group to root o Change mode to 640 or more restrictive • - IF - /etc/at.deny exists: o Change owner or user root o If group daemon exists, change to group daemon, else change group to root o Change mode to 640 or more restrictive #!/usr/bin/env bash { grep -Pq -- '^daemon\b' /etc/group && l_group="daemon" || l_group="root" [ ! -e "/etc/at.allow" ] && touch /etc/at.allow chown root:"$l_group" /etc/at.allow chmod u-x,g-wx,o-rwx /etc/at.allow [ -e "/etc/at.deny" ] && chown root:"$l_group" /etc/at.deny [ -e "/etc/at.deny" ] && chmod u-x,g-wx,o-rwx /etc/at.deny } References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 328 Internal Only - General 3 Network This section provides guidance on for securing the network configuration of the system Page 329 Internal Only - General 3.1 Configure Network Devices To reduce the attack surface of a system, unused devices should be disabled. Note: This should not be considered a comprehensive list, you may wish to consider additions to those listed here for your environment. Page 330 Internal Only - General 3.1.1 Ensure IPv6 status is identified (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Internet Protocol Version 6 (IPv6) is the most recent version of Internet Protocol (IP). It's designed to supply IP addressing and additional security to support the predicted growth of connected devices. IPv6 is based on 128-bit addressing and can support 340 undecillion, which is 340,282,366,920,938,463,463,374,607,431,768,211,456 unique addresses. Features of IPv6 • Hierarchical addressing and routing infrastructure • Statefull and Stateless configuration • Support for quality of service (QoS) • An ideal protocol for neighboring node interaction Rationale: IETF RFC 4038 recommends that applications are built with an assumption of dual stack. It is recommended that IPv6 be enabled and configured in accordance with Benchmark recommendations. - IF - dual stack and IPv6 are not used in your environment, IPv6 may be disabled to reduce the attack surface of the system, and recommendations pertaining to IPv6 can be skipped. Note: It is recommended that IPv6 be enabled and configured unless this is against local site policy Impact: IETF RFC 4038 recommends that applications are built with an assumption of dual stack. When enabled, IPv6 will require additional configuration to reduce risk to the system. Page 331 Internal Only - General Audit: Run the following script to identify if IPv6 is enabled on the system: #!/usr/bin/env bash { l_output="" ! grep -Pqs -- '^\h*0\b' /sys/module/ipv6/parameters/disable && l_output="- IPv6 is not enabled" if sysctl net.ipv6.conf.all.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\b" && \ sysctl net.ipv6.conf.default.disable_ipv6 | grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\b"; then l_output="- IPv6 is not enabled" fi [ -z "$l_output" ] && l_output="- IPv6 is enabled" echo -e "\n$l_output\n" } Remediation: Enable or disable IPv6 in accordance with system requirements and local site policy Default Value: IPv6 is enabled References: 1. NIST SP 800-53 Rev. 5: CM-7 Additional Information: Having more addresses has grown in importance with the expansion of smart devices and connectivity. IPv6 provides more than enough globally unique IP addresses for every networked device currently on the planet, helping ensure providers can keep pace with the expected proliferation of IP-based devices. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 332 Internal Only - General 3.1.2 Ensure wireless interfaces are not available (Automated) Profile Applicability: • Level 1 - Server Description: Wireless networking is used when wired networks are unavailable. Rationale: -IF- wireless is not to be used, wireless devices can be disabled to reduce the potential attack surface. Impact: Many if not all laptop workstations and some desktop workstations will connect via wireless requiring these interfaces be enabled. Audit: Run the following script to verify no wireless interfaces are active on the system: Page 333 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" module_chk() { # Check how module will be loaded l_loadable="$(modprobe -n -v "$l_mname")" if grep -Pq -- '^\h*install \/bin\/(true|false)' <<< "$l_loadable"; then l_output="$l_output\n - module: \"$l_mname\" is not loadable: \"$l_loadable\"" else l_output2="$l_output2\n - module: \"$l_mname\" is loadable: \"$l_loadable\"" fi # Check is the module currently loaded if ! lsmod | grep "$l_mname" > /dev/null 2>&1; then l_output="$l_output\n - module: \"$l_mname\" is not loaded" else l_output2="$l_output2\n - module: \"$l_mname\" is loaded" fi # Check if the module is deny listed if modprobe --showconfig | grep -Pq -- "^\h*blacklist\h+$l_mname\b"; then l_output="$l_output\n - module: \"$l_mname\" is deny listed in: \"$(grep -Pl -- "^\h*blacklist\h+$l_mname\b" /etc/modprobe.d/*)\"" else l_output2="$l_output2\n - module: \"$l_mname\" is not deny listed" fi } if [ -n "$(find /sys/class/net/*/ -type d -name wireless)" ]; then l_dname=$(for driverdir in $(find /sys/class/net/*/ -type d -name wireless | xargs -0 dirname); do basename "$(readlink -f "$driverdir"/device/driver/module)";done | sort -u) for l_mname in $l_dname; do module_chk done fi # Report results. If no failures output in l_output2, we pass if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **" if [ -z "$l_output" ]; then echo -e "\n - System has no wireless NICs installed" else echo -e "\n$l_output\n" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit failure:\n$l_output2\n" [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n" fi } Page 334 Internal Only - General Remediation: Run the following command to disable any wireless interfaces: # find /lib/modules/`uname -r`/kernel/drivers/net/wireless -name '*.ko' - printf 'install %f /bin/false\nblacklist %f\n\n' | sed 's/\.ko//1' >> /etc/modprobe.d/blacklist-wireless.conf Note: the *.conf file in /etc/modprobe.d/ in the above command can renamed as needed. References: 1. NIST SP 800-53 Rev. 5: CM-7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 15.4 Disable Wireless Access on Devices if Not Required v7 Disable wireless access on devices that do not have a business purpose for ● wireless access. 15.5 Limit Wireless Access on Client Devices v7 Configure wireless access on client machines that do have an essential wireless business purpose, to allow access only to authorized wireless networks ● and to restrict access to other wireless networks. Page 335 Internal Only - General 3.1.3 Ensure bluetooth services are not in use (Automated) Profile Applicability: • Level 1 - Server • Level 2 - Workstation Description: Bluetooth is a short-range wireless technology standard that is used for exchanging data between devices over short distances. It employs UHF radio waves in the ISM bands, from 2.402 GHz to 2.48 GHz. It is mainly used as an alternative to wire connections. Rationale: An attacker may be able to find a way to access or corrupt your data. One example of this type of activity is bluesnarfing, which refers to attackers using a Bluetooth connection to steal information off of your Bluetooth device. Also, viruses or other malicious code can take advantage of Bluetooth technology to infect other devices. If you are infected, your data may be corrupted, compromised, stolen, or lost. Impact: Many personal electronic devices (PEDs) use Bluetooth technology. For example, you may be able to operate your computer with a wireless keyboard. Disabling Bluetooth will prevent these devices from connecting to the system. There may be packages that are dependent on the bluez package. If the bluez package is removed, these dependent packages will be removed as well. Before removing the bluez package, review any dependent packages to determine if they are required on the system. -IF- a dependent package is required: stop and mask bluetooth.service leaving the bluez package installed. Page 336 Internal Only - General Audit: Run the following command to verify the bluez package is not installed: # dpkg-query -s bluez &>/dev/null && echo "bluez is installed" Nothing should be returned. - OR - - IF - the bluez package is required as a dependency: Run the following command to verify bluetooth.service is not enabled: # systemctl is-enabled bluetooth.service 2>/dev/null | grep 'enabled' Nothing should be returned. Run the following command to verify bluetooth.service is not active: # systemctl is-active bluetooth.service 2>/dev/null | grep '^active' Nothing should be returned. Note: If the package is required for a dependency • Ensure the dependent package is approved by local site policy • Ensure stopping and masking the service and/or socket meets local site policy Remediation: Run the following commands to stop bluetooth.service, and remove the bluez package: # systemctl stop bluetooth.service # apt purge bluez - OR - - IF - the bluez package is required as a dependency: Run the following commands to stop and mask bluetooth.service: # systemctl stop bluetooth.service # systemctl mask bluetooth.service Note: A reboot may be required References: 1. https://www.cisa.gov/tips/st05-015 2. NIST SP 800-53 Rev. 5: CM-7 Page 337 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 338 Internal Only - General 3.2 Configure Network Kernel Modules The Linux kernel modules support several network protocols that are not commonly used. If these protocols are not needed, it is recommended that they be disabled in the kernel. Note: This should not be considered a comprehensive list of uncommon network protocols, you may wish to consider additions to those listed here for your environment. Page 339 Internal Only - General 3.2.1 Ensure dccp kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Datagram Congestion Control Protocol (DCCP) is a transport layer protocol that supports streaming media and telephony. DCCP provides a way to gain access to congestion control, without having to do it at the application layer, but does not provide in-sequence delivery. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the dccp kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the dccp kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="dccp" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the dccp kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the dccp filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 340 Internal Only - General 2. verify the dccp kernel module is not loaded and not loadable by performing the following: Run the following command to verify the dccp kernel module is not loaded: # lsmod | grep 'dccp' Nothing should be returned Run the following command to verify the dccp kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+dccp\b' Verify the output includes: blacklist dccp -AND- install dccp /bin/false -OR- install dccp /bin/true Example output: blacklist dccp install dccp /bin/false Remediation: Unload and disable the dccp kernel module. 1. Run the following commands to unload the dccp kernel module: # modprobe -r dccp 2>/dev/null # rmmod dccp 2>/dev/null 2. Perform the following to disable the dccp kernel module: Create a file ending in .conf with install dccp /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install dccp /bin/false" >> /etc/modprobe.d/60-dccp.conf Create a file ending in .conf with blacklist dccp in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist dccp" >> /etc/modprobe.d/60-dccp.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 341 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 342 Internal Only - General 3.2.2 Ensure tipc kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communication between cluster nodes. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the tipc kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the tipc kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="tipc" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the tipc kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the tipc filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: 2. verify the tipc kernel module is not loaded and not loadable by performing the following: Run the following command to verify the tipc kernel module is not loaded: # lsmod | grep 'tipc' Nothing should be returned Page 343 Internal Only - General Run the following command to verify the tipc kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+tipc\b' Verify the output includes: blacklist tipc -AND- install tipc /bin/false -OR- install tipc /bin/true Example output: blacklist tipc install tipc /bin/false Remediation: Unload and disable the tipc kernel module. 1. Run the following commands to unload the tipc kernel module: # modprobe -r tipc 2>/dev/null # rmmod tipc 2>/dev/null 2. Perform the following to disable the tipc kernel module: Create a file ending in .conf with install tipc /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install tipc /bin/false" >> /etc/modprobe.d/60-tipc.conf Create a file ending in .conf with blacklist tipc in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist tipc" >> /etc/modprobe.d/60-tipc.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040024 | RULE ID: SV-230497r1069313 | CAT III 5. STIG ID: OL08-00-040024 | RULE ID: SV-248832r958478 | CAT III 6. STIG ID: RHEL-09-213065 | RULE ID: SV-257808r1044865 | CAT II 7. STIG ID: ALMA-09-030270 | RULE ID: SV-269347r1050229 | CAT II 8. STIG ID: OL09-00-000044 | RULE ID: SV-271447r1092464 | CAT II Page 344 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 345 Internal Only - General 3.2.3 Ensure rds kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Reliable Datagram Sockets (RDS) protocol is a transport layer protocol designed to provide low-latency, high-bandwidth communications between cluster nodes. It was developed by the Oracle Corporation. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the rds kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the rds kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="rds" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the rds kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the rds filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 346 Internal Only - General 2. verify the rds kernel module is not loaded and not loadable by performing the following: Run the following command to verify the rds kernel module is not loaded: # lsmod | grep 'rds' Nothing should be returned Run the following command to verify the rds kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+rds\b' Verify the output includes: blacklist rds -AND- install rds /bin/false -OR- install rds /bin/true Example output: blacklist rds install rds /bin/false Remediation: Unload and disable the rds kernel module. 1. Run the following commands to unload the rds kernel module: # modprobe -r rds 2>/dev/null # rmmod rds 2>/dev/null 2. Perform the following to disable the rds kernel module: Create a file ending in .conf with install rds /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install rds /bin/false" >> /etc/modprobe.d/60-rds.conf Create a file ending in .conf with blacklist rds in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist rds" >> /etc/modprobe.d/60-rds.conf References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) Page 347 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 348 Internal Only - General 3.2.4 Ensure sctp kernel module is not available (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Stream Control Transmission Protocol (SCTP) is a transport layer protocol used to support message oriented communication, with several streams of messages in one connection. It serves a similar function as TCP and UDP, incorporating features of both. It is message-oriented like UDP, and ensures reliable in-sequence transport of messages with congestion control like TCP. Rationale: Removing support for unneeded protocols reduces the local attack surface of the system. If this protocol is not needed, disable it. Audit: Verify the sctp kernel module is not available on the system or has been disabled. 1. Run the following script to determine if the sctp kernel module is available on the system: #!/usr/bin/env bash { l_mod_name="sctp" l_mod_type="net" while IFS= read -r l_mod_path; do if [ -d "$l_mod_path/${l_mod_name//-/\/}" ] && \ [ -n "$(ls -A "$l_mod_path/${l_mod_name//-/\/}")" ]; then printf '%s\n' "$l_mod_name exists in $l_mod_path" fi done < <(readlink -e /usr/lib/modules/**/kernel/$l_mod_type \ || readlink -e /lib/modules/**/kernel/$l_mod_type) } If nothing is returned, the sctp kernel module is not available on the system and no further audit steps are required. Note: Some systems may include the sctp filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state. If anything is returned by the above script: Page 349 Internal Only - General 2. verify the sctp kernel module is not loaded and not loadable by performing the following: Run the following command to verify the sctp kernel module is not loaded: # lsmod | grep 'sctp' Nothing should be returned Run the following command to verify the sctp kernel module is not loadable: # modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+sctp\b' Verify the output includes: blacklist sctp -AND- install sctp /bin/false -OR- install sctp /bin/true Example output: blacklist sctp install sctp /bin/false Remediation: Unload and disable the sctp kernel module. 1. Run the following commands to unload the sctp kernel module: # modprobe -r sctp 2>/dev/null # rmmod sctp 2>/dev/null 2. Perform the following to disable the sctp kernel module: Create a file ending in .conf with install sctp /bin/false in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "install sctp /bin/false" >> /etc/modprobe.d/60-sctp.conf Create a file ending in .conf with blacklist sctp in the /etc/modprobe.d/ directory Example: # printf '\n%s\n' "blacklist sctp" >> /etc/modprobe.d/60-sctp.conf Page 350 Internal Only - General References: 1. CCI-000381 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (ii) 4. STIG ID: RHEL-08-040023 | RULE ID: SV-230496r1069312 | CAT III 5. STIG ID: OL08-00-040023 | RULE ID: SV-248831r991589 | CAT II 6. STIG ID: RHEL-09-213060 | RULE ID: SV-257807r1044862 | CAT II 7. STIG ID: ALMA-09-030050 | RULE ID: SV-269345r1050227 | CAT II 8. STIG ID: OL09-00-000043 | RULE ID: SV-271446r1091050 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 351 Internal Only - General 3.3 Configure Network Kernel Parameters This section contains Recommendations covering kernel parameters effecting network stack. Note: • Some of the Recommendations in this section's subsections are not applicable if the system is a router. These Recommendations include a note in their description. • sysctl settings are defined through files in /usr/local/lib, /usr/lib/, /lib/, /run/, and /etc/ • Files are typically placed in the sysctl.d directory within the parent directory • The paths where sysctl preload files usually exist o /run/sysctl.d/*.conf o /etc/sysctl.d/*.conf o /usr/local/lib/sysctl.d/*.conf o /usr/lib/sysctl.d/*.conf o /lib/sysctl.d/*.conf o /etc/sysctl.conf • Files must have the ".conf" extension • Vendors settings usually live in /usr/lib/ or /usr/local/lib/ • To override a whole file, create a new file with the same name in /etc/sysctl.d/ and put new settings there. • To override only specific settings, add a file with a lexically later name in /etc/sysctl.d/ and put new settings there. • The command /usr/lib/systemd/systemd-sysctl --cat-config produces output containing The system's loaded kernel parameters and the files they're configured in: o Entries listed latter in the file take precedence over the same settings listed earlier in the file o Files containing kernel parameters that are over-ridden by other files with the same name will not be listed o On systems running UncomplicatedFirewall, the kernel parameters may be set or over-written. This will not be visible in the output of the command • On systems with Uncomplicated Firewall, additional settings may be configured in /etc/ufw/sysctl.conf o The settings in /etc/ufw/sysctl.conf will override settings other settings and will not be visible in the output of the /usr/lib/systemd/systemd-sysctl --cat-config command o This behavior can be changed by updating the IPT_SYSCTL parameter in /etc/default/ufw Page 352 Internal Only - General 3.3.1 Configure IPv4 parameters net.ipv4 kernel parameters control various aspects of the IPv4 network stack. These parameters effect functions to include routing, TCP, and security. Page 353 Internal Only - General 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The net.ipv4.ip_forward flag tells the system whether it can forward IPv4 packets or not. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.conf.all.forwarding=0 and net.ipv4.conf.default.forwarding=0 are configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Setting net.ipv4.ip_forward to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will not be able to forward IPv4 packets. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Audit: Verify net.ipv4.ip_forward is set to 0. 1. Run the following command to verify net.ipv4.ip_forward is set to 0 in the running configuration: # sysctl net.ipv4.ip_forward Verify output is: net.ipv4.ip_forward = 0 2. Run the following script to verify net.ipv4.ip_forward = 0 is set in a file being used by systemd sysctl to configure net.ipv4.ip_forward: Page 354 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.ip_forward" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.ip_forward = 0" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 355 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.ip_forward lines that are not net.ipv4.ip_forward=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.ip_forward" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 356 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.ip_forward = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.ip_forward = 0" >> /etc/sysctl.d/60- ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.ip_forward = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: SLES-15-040380 | RULE ID: SV-235024r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 357 Internal Only - General 3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.all.forwarding controls forwarding of IPv4 packet on all interfaces. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.ip_forward=0 is configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Cloud Service Provider (CSP) hosted systems may require forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IPv4 forwarding. Page 358 Internal Only - General Audit: Verify net.ipv4.conf.all.forwarding is set to 0. 1. Run the following command to verify net.ipv4.conf.all.forwarding is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.forwarding Verify output is: net.ipv4.conf.all.forwarding = 0 2. Run the following script to verify net.ipv4.conf.all.forwarding = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.forwarding: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 359 Internal Only - General Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 360 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.forwarding lines that are not net.ipv4.conf.all.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.forwarding = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Page 361 Internal Only - General Default Value: net.ipv4.conf.all.forwarding = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040259 | RULE ID: SV-250317r1017358 | CAT II 5. STIG ID: OL08-00-040259 | RULE ID: SV-252662r991589 | CAT II 6. STIG ID: RHEL-09-253075 | RULE ID: SV-257970r1045011 | CAT II 7. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 8. STIG ID: OL09-00-006028 | RULE ID: SV-271872r1092328 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 362 Internal Only - General 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.default.forwarding controls forwarding of IPv4 packet on newly added network interfaces. Note: • If this system is a router this recommendation is not applicable. • If net.ipv4.ip_forward=0 is configured, this recommendation may be skipped. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Cloud Service Provider (CSP) hosted systems may require forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IPv4 forwarding. Page 363 Internal Only - General Audit: Verify net.ipv4.conf.default.forwarding is set to 0. 1. Run the following command to verify net.ipv4.conf.default.forwarding is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.forwarding Verify output is: net.ipv4.conf.default.forwarding = 0 2. Run the following script to verify net.ipv4.conf.default.forwarding = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.forwarding: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 364 Internal Only - General Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 365 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.forwarding lines that are not net.ipv4.conf.default.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.forwarding = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Page 366 Internal Only - General Default Value: net.ipv4.conf.default.forwarding = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 367 Internal Only - General 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.all.send_redirects controls sending of all IPv4 ICMP redirected packets on all interfaces. Note: If this system is a router this recommendation is not applicable. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Page 368 Internal Only - General Audit: Verify net.ipv4.conf.all.send_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.send_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.send_redirects Verify output is: net.ipv4.conf.all.send_redirects = 0 2. Run the following script to verify net.ipv4.ip_forward = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.send_redirects: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.send_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.send_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 369 Internal Only - General Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 370 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.send_redirects lines that are not net.ipv4.conf.all.send_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.send_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.send_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.send_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Page 371 Internal Only - General Default Value: net.ipv4.conf.all.send_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040220 | RULE ID: SV-230536r1017298 | CAT II 5. STIG ID: OL08-00-040220 | RULE ID: SV-248877r991589 | CAT II 6. STIG ID: RHEL-09-253065 | RULE ID: SV-257968r991589 | CAT II 7. STIG ID: ALMA-09-019930 | RULE ID: SV-269256r1050138 | CAT II 8. STIG ID: OL09-00-006032 | RULE ID: SV-271875r1092337 | CAT II 9. STIG ID: SLES-15-040370 | RULE ID: SV-235023r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 372 Internal Only - General 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. net.ipv4.conf.default.send_redirects controls sending of all IPv4 ICMP redirected packets on a newly added network interface. Note: If this system is a router this recommendation is not applicable. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Page 373 Internal Only - General Audit: Verify net.ipv4.conf.default.send_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.send_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.send_redirects Verify output is: net.ipv4.conf.default.send_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.send_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.send_redirects: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.send_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.send_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Page 374 Internal Only - General Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Page 375 Internal Only - General Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.send_redirects lines that are not net.ipv4.conf.default.send_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.send_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.send_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.send_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Page 376 Internal Only - General Default Value: net.ipv4.conf.default.send_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040270 | RULE ID: SV-230543r1017305 | CAT II 5. STIG ID: OL08-00-040270 | RULE ID: SV-248886r991589 | CAT II 6. STIG ID: RHEL-09-253070 | RULE ID: SV-257969r991589 | CAT II 7. STIG ID: ALMA-09-019930 | RULE ID: SV-269256r1050138 | CAT II 8. STIG ID: OL09-00-006033 | RULE ID: SV-271876r1092641 | CAT II 9. STIG ID: SLES-15-040360 | RULE ID: SV-235022r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 377 Internal Only - General 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.icmp_ignore_bogus_error_responses controls if the kernel logs bogus responses (RFC-1122 non-compliant) from broadcast reframes. Rationale: Some routers (and some attackers) will send responses that violate RFC-1122 and attempt to fill up a log file system with many useless error messages. Audit: Verify net.ipv4.icmp_ignore_bogus_error_responses is set to 1. 1. Run the following command to verify net.ipv4.icmp_ignore_bogus_error_responses is set to 1 in the running configuration: # sysctl net.ipv4.icmp_ignore_bogus_error_responses Verify output is: net.ipv4.icmp_ignore_bogus_error_responses = 1 2. Run the following script to verify net.ipv4.icmp_ignore_bogus_error_responses = 1 is set in a file being used by systemd sysctl to configure net.ipv4.icmp_ignore_bogus_error_responses: Page 378 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.icmp_ignore_bogus_error_responses" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.icmp_ignore_bogus_error_responses = 1" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 379 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.icmp_ignore_bogus_error_responses lines that are not net.ipv4.icmp_ignore_bogus_error_responses=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.icmp_ignore_bogus_error_responses" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 380 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.icmp_ignore_bogus_error_responses = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.icmp_ignore_bogus_error_responses = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.icmp_ignore_bogus_error_responses = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253060 | RULE ID: SV-257967r991589 | CAT II 5. STIG ID: ALMA-09-018940 | RULE ID: SV-269247r1050129 | CAT II 6. STIG ID: OL09-00-006031 | RULE ID: SV-271874r1092612 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 381 Internal Only - General 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.icmp_echo_ignore_broadcasts controls if all ICMP echo and timestamp requests to broadcast and multicast addresses are ignored. Rationale: Accepting ICMP echo and timestamp requests with broadcast or multicast destinations for your network could be used to trick your host into starting (or participating) in a Smurf attack. A Smurf attack relies on an attacker sending large amounts of ICMP broadcast messages with a spoofed source address. All hosts receiving this message and responding would send echo-reply messages back to the spoofed address, which is probably not routable. If many hosts respond to the packets, the amount of traffic on the network could be significantly multiplied. Audit: Verify net.ipv4.icmp_echo_ignore_broadcasts is set to 1. 1. Run the following command to verify net.ipv4.icmp_echo_ignore_broadcasts is set to 1 in the running configuration: # sysctl net.ipv4.icmp_echo_ignore_broadcasts Verify output is: net.ipv4.icmp_echo_ignore_broadcasts = 1 2. Run the following script to verify net.ipv4.icmp_echo_ignore_broadcasts = 1 is set in a file being used by systemd sysctl to configure net.ipv4.icmp_echo_ignore_broadcasts: Page 382 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.icmp_echo_ignore_broadcasts" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.icmp_echo_ignore_broadcasts = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 383 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.icmp_echo_ignore_broadcasts lines that are not net.ipv4.icmp_echo_ignore_broadcasts=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.icmp_echo_ignore_broadcasts" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 384 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.icmp_echo_ignore_broadcasts = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.icmp_echo_ignore_broadcasts = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.icmp_echo_ignore_broadcasts = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040230 | RULE ID: SV-230537r1017299 | CAT II 5. STIG ID: OL08-00-040230 | RULE ID: SV-248878r991589 | CAT II 6. STIG ID: RHEL-09-253055 | RULE ID: SV-257966r991589 | CAT II 7. STIG ID: ALMA-09-019050 | RULE ID: SV-269248r1050130 | CAT II 8. STIG ID: OL09-00-006030 | RULE ID: SV-271873r1092331 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 385 Internal Only - General 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv4.conf.all.accept_redirects controls accepting of all IPv4 ICMP redirected packets on all interfaces. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will not accept any IPv4 ICMP redirect messages, and therefore, won't allow outsiders to update the system's routing tables. Audit: Verify net.ipv4.conf.all.accept_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.accept_redirects Verify output is: net.ipv4.conf.all.accept_redirects = 0 2. Run the following script to verify net.ipv4.conf.all.send_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.send_redirects: Page 386 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 387 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.accept_redirects lines that are not net.ipv4.conf.all.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 388 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.all.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040279 | RULE ID: SV-244553r1017353 | CAT II 5. STIG ID: OL08-00-040279 | RULE ID: SV-248887r991589 | CAT II 6. STIG ID: RHEL-09-253015 | RULE ID: SV-257958r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006020 | RULE ID: SV-271864r1092304 | CAT II 9. STIG ID: SLES-15-040330 | RULE ID: SV-235018r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 389 Internal Only - General 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv4.conf.default.accept_redirects controls accepting of all IPv4 ICMP redirected packets on a newly added network interface. Note: If this system is a router this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv4.conf.all.accept_redirects to 0, the system will not accept IPv4 ICMP redirect messages on a newly added network interface. Audit: Verify net.ipv4.conf.default.accept_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.accept_redirects Verify output is: net.ipv4.conf.default.accept_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.accept_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.accept_redirects: Page 390 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 391 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.accept_redirects lines that are not net.ipv4.conf.default.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 392 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.default.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040209 | RULE ID: SV-244550r1017350 | CAT II 5. STIG ID: OL08-00-040209 | RULE ID: SV-248875r991589 | CAT II 6. STIG ID: RHEL-09-253040 | RULE ID: SV-257963r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006025 | RULE ID: SV-271869r1092319 | CAT II 9. STIG ID: SLES-15-040340 | RULE ID: SV-235019r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 393 Internal Only - General 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure. Rationale: It is still possible for even known gateways to be compromised. Setting net.ipv4.conf.all.secure_redirects to 0 the system will not accept any IPv4 routing table updates by possibly compromised known gateways. Audit: Verify net.ipv4.conf.all.secure_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.all.secure_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.secure_redirects Verify output is: net.ipv4.conf.all.secure_redirects = 0 2. Run the following script to verify net.ipv4.conf.all.secure_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.secure_redirects: Page 394 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.secure_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.secure_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 395 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.secure_redirects lines that are not net.ipv4.conf.all.secure_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.secure_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 396 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.secure_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.secure_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.all.secure_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 397 Internal Only - General 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure. Rationale: It is still possible for even known gateways to be compromised. Setting net.ipv4.conf.default.secure_redirects to 0 the system the system will not accept IPv4 routing table updates by possibly compromised known gateways on a newly added network interface. Audit: Verify net.ipv4.conf.default.secure_redirects is set to 0. 1. Run the following command to verify net.ipv4.conf.default.secure_redirects is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.secure_redirects Verify output is: net.ipv4.conf.default.secure_redirects = 0 2. Run the following script to verify net.ipv4.conf.default.secure_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.secure_redirects: Page 398 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.secure_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.secure_redirects = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 399 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.secure_redirects lines that are not net.ipv4.conf.default.secure_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.secure_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 400 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.secure_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.secure_redirects = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.default.secure_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 401 Internal Only - General 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.conf.all.rp_filter controls reverse path filtering for IPv4 traffic on all network interfaces. Reverse path filtering is a security mechanism in Linux that helps prevent IP spoofing and other network attacks. When enabled, it checks if the source IP address of an incoming packet is reachable through the same network interface it was received on. If the packet's source address is not reachable through the interface it arrived on, the packet is dropped. Note: If this system is a router, and uses asymmetrical routing, this recommendation is not applicable. Rationale: Setting net.ipv4.conf.all.rp_filter to 1 is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Impact: If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Audit: Verify net.ipv4.conf.all.rp_filter is set to 1. 1. Run the following command to verify net.ipv4.conf.all.rp_filter is set to 1 in the running configuration: # sysctl net.ipv4.conf.all.rp_filter Verify output is: net.ipv4.conf.all.rp_filter = 1 2. Run the following script to verify net.ipv4.conf.all.rp_filter = 1 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.rp_filter: Page 402 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.rp_filter" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.rp_filter = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 403 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.rp_filter lines that are not net.ipv4.conf.all.rp_filter=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.rp_filter" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 404 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.rp_filter = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.rp_filter = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.all.rp_filter = 2 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040285 | RULE ID: SV-230549r1017311 | CAT II 5. STIG ID: OL08-00-040285 | RULE ID: SV-248893r991589 | CAT II 6. STIG ID: RHEL-09-253035 | RULE ID: SV-257962r991589 | CAT II 7. STIG ID: ALMA-09-019820 | RULE ID: SV-269255r1050137 | CAT II 8. STIG ID: OL09-00-006024 | RULE ID: SV-271868r1092316 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 405 Internal Only - General 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: net.ipv4.conf.default.rp_filter controls reverse path filtering for IPv4 traffic on newly added network interfaces. Reverse path filtering is a security mechanism in Linux that helps prevent IP spoofing and other network attacks. When enabled, it checks if the source IP address of an incoming packet is reachable through the same network interface it was received on. If the packet's source address is not reachable through the interface it arrived on, the packet is dropped. Note: If this system is a router, and uses asymmetrical routing, this recommendation is not applicable. Rationale: Setting net.ipv4.conf.default.rp_filter to 1 is a good way to deter attackers from sending your system bogus packets that cannot be responded to. One instance where this feature breaks down is if asymmetrical routing is employed. This would occur when using dynamic routing protocols (bgp, ospf, etc) on your system. If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Impact: If you are using asymmetrical routing on your system, you will not be able to enable this feature without breaking the routing. Audit: Verify net.ipv4.conf.default.rp_filter is set to 1. 1. Run the following command to verify net.ipv4.conf.default.rp_filter is set to 1 in the running configuration: # sysctl net.ipv4.conf.default.rp_filter Verify output is: net.ipv4.conf.default.rp_filter = 1 Page 406 Internal Only - General 2. Run the following script to verify net.ipv4.conf.default.rp_filter = 1 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.rp_filter: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.rp_filter" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.rp_filter = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 407 Internal Only - General SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.rp_filter lines that are not net.ipv4.conf.default.rp_filter=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.rp_filter" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 408 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.rp_filter = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.rp_filter = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.default.rp_filter = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253050 | RULE ID: SV-257965r991589 | CAT II 5. STIG ID: ALMA-09-019820 | RULE ID: SV-269255r1050137 | CAT II 6. STIG ID: OL09-00-006027 | RULE ID: SV-271871r1092325 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 409 Internal Only - General 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv4.conf.all.accept_source_route controls accepting of all IPv4 packets with the SSR or LSR option set on all interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. Rationale: Setting net.ipv4.conf.all.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: Verify net.ipv4.conf.all.accept_source_route is set to 0. 1. Run the following command to verify net.ipv4.conf.all.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv4.conf.all.accept_source_route Verify output is: net.ipv4.conf.all.accept_source_route = 0 Page 410 Internal Only - General 2. Run the following script to verify net.ipv4.conf.all.accept_source_route = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.accept_source_route = 0" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • Page 411 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.accept_source_route lines that are not net.ipv4.conf.all.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 412 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.all.accept_source_route = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040239 | RULE ID: SV-244551r1017351 | CAT II 5. STIG ID: OL08-00-040239 | RULE ID: SV-248879r991589 | CAT II 6. STIG ID: RHEL-09-253020 | RULE ID: SV-257959r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006021 | RULE ID: SV-271865r1092307 | CAT II 9. STIG ID: SLES-15-040300 | RULE ID: SV-235014r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 413 Internal Only - General 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv4.conf.default.accept_source_route controls accepting of all IPv4 packets with the SSR or LSR option set on newly added network interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. Rationale: Setting net.ipv4.conf.default.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: Verify net.ipv4.conf.default.accept_source_route is set to 0. 1. Run the following command to verify net.ipv4.conf.default.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv4.conf.default.accept_source_route Verify output is: net.ipv4.conf.default.accept_source_route = 0 Page 414 Internal Only - General 2. Run the following script to verify net.ipv4.conf.default.accept_source_route = 0 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.accept_source_route = 0" is set in: "/etc/sysctl.d/60-ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 415 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.accept_source_route lines that are not net.ipv4.conf.default.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 416 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.default.accept_source_route = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040249 | RULE ID: SV-244552r1017352 | CAT II 5. STIG ID: OL08-00-040249 | RULE ID: SV-248881r991589 | CAT II 6. STIG ID: RHEL-09-253045 | RULE ID: SV-257964r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006026 | RULE ID: SV-271870r1092322 | CAT II 9. STIG ID: SLES-15-040320 | RULE ID: SV-235016r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 417 Internal Only - General 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When enabled, this feature logs packets with un-routable source addresses to the kernel log. net.ipv4.conf.all.log_martians controls if IPv4 packets with un-routable source addresses on any network interface is logged to the kernel log. Rationale: Setting net.ipv4.conf.all.log_martians to 1 enables this feature. Logging these packets allows an administrator to investigate the possibility that an attacker is sending spoofed packets to their system. Audit: Verify net.ipv4.conf.all.log_martians is set to 1. 1. Run the following command to verify net.ipv4.conf.all.log_martians is set to 1 in the running configuration: # sysctl net.ipv4.conf.all.log_martians Verify output is: net.ipv4.conf.all.log_martians = 1 2. Run the following script to verify net.ipv4.conf.all.log_martians = 1 is set in a file being used by systemd sysctl to configure net.ipv4.conf.all.log_martians: Page 418 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.all.log_martians" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.all.log_martians = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 419 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.all.log_martians lines that are not net.ipv4.conf.all.log_martians=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.all.log_martians" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 420 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.all.log_martians = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.all.log_martians = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.all.log_martians = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253025 | RULE ID: SV-257960r991589 | CAT II 5. STIG ID: ALMA-09-019380 | RULE ID: SV-269251r1050133 | CAT II 6. STIG ID: OL09-00-006022 | RULE ID: SV-271866r1092310 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 421 Internal Only - General 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When enabled, this feature logs packets with un-routable source addresses to the kernel log. net.ipv4.conf.default.log_martians controls if IPv4 packets with un-routable source addresses on a newly added network interface is logged to the kernel log. Rationale: Setting net.ipv4.conf.default.log_martians to 1 enables this feature. Logging these packets allows an administrator to investigate the possibility that an attacker is sending spoofed packets to their system. Audit: Verify net.ipv4.conf.default.log_martians is set to 1. 1. Run the following command to verify net.ipv4.conf.default.log_martians is set to 1 in the running configuration: # sysctl net.ipv4.conf.default.log_martians Verify output is: net.ipv4.conf.default.log_martians = 1 2. Run the following script to verify net.ipv4.conf.default.log_martians = 1 is set in a file being used by systemd sysctl to configure net.ipv4.conf.default.log_martians: Page 422 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.conf.default.log_martians" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.conf.default.log_martians = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 423 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.conf.default.log_martians lines that are not net.ipv4.conf.default.log_martians=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.conf.default.log_martians" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 424 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.conf.default.log_martians = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.conf.default.log_martians = 1" \ >> /etc/sysctl.d/60-ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.conf.default.log_martians = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-09-253030 | RULE ID: SV-257961r991589 | CAT II 5. STIG ID: ALMA-09-019380 | RULE ID: SV-269251r1050133 | CAT II 6. STIG ID: OL09-00-006023 | RULE ID: SV-271867r1092313 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 425 Internal Only - General 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: When tcp_syncookies is set, the kernel will handle TCP SYN packets normally until the half-open connection queue is full, at which time, the SYN cookie functionality kicks in. SYN cookies work by not using the SYN queue at all. Instead, the kernel simply replies to the SYN with a SYN/ACK, but will include a specially crafted TCP sequence number that encodes the source and destination IP address and port number and the time the packet was sent. A legitimate connection would send the ACK packet of the three way handshake with the specially crafted sequence number. This allows the system to verify that it has received a valid response to a SYN cookie and allow the connection, even though there is no corresponding SYN in the queue. Rationale: Attackers use SYN flood attacks to perform a denial of service attacked on a system by sending many SYN packets without completing the three way handshake. This will quickly use up slots in the kernel's half-open connection queue and prevent legitimate connections from succeeding. Setting net.ipv4.tcp_syncookies to 1 enables SYN cookies, allowing the system to keep accepting valid connections, even if under a denial of service attack. Audit: Verify net.ipv4.tcp_syncookies is set to 1. 1. Run the following command to verify net.ipv4.tcp_syncookies is set to 1 in the running configuration: # sysctl net.ipv4.tcp_syncookies Verify output is: net.ipv4.tcp_syncookies = 1 2. Run the following script to verify net.ipv4.tcp_syncookies = 1 is set in a file being used by systemd sysctl to configure net.ipv4.tcp_syncookies: Page 426 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv4.tcp_syncookies" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv4.tcp_syncookies = 1" is set in: "/etc/sysctl.d/60- ipv4_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 427 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv4.tcp_syncookies lines that are not net.ipv4.tcp_syncookies=1. Example script: #!/usr/bin/env bash { l_option="net.ipv4.tcp_syncookies" l_value="1" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(0|[2-9]|1[0-9]+)/s/^/# /' "$l_file" done } Page 428 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv4.tcp_syncookies = 1 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv4.tcp_syncookies = 1" >> /etc/sysctl.d/60- ipv4_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv4.tcp_syncookies = 1 References: 1. CCI-001095 | CCI-002385 2. NIST SP 800-53 :: SC-5 (2) | NIST SP 800-53 :: SC-5 a 3. NIST SP 800-53A :: SC-5 (2).1 4. STIG ID: RHEL-09-253010 | RULE ID: SV-257957r1045009 | CAT II 5. STIG ID: ALMA-09-042480 | RULE ID: SV-269435r1050318 | CAT II 6. STIG ID: OL09-00-006050 | RULE ID: SV-271884r1092364 | CAT II 7. STIG ID: UBTU-22-253010 | RULE ID: SV-260522r1069097 | CAT II 8. STIG ID: UBTU-24-600190 | RULE ID: SV-270753r1066748 | CAT II 9. STIG ID: SLES-15-010310 | RULE ID: SV-234829r958528 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 429 Internal Only - General 3.3.2 Configure IPv6 parameters net.ipv6 kernel parameters control various aspects of the IPv6 network stack. These parameters effect functions to include routing, TCP, and security. Note: If IPv6 has been disabled on the system, the Recommendations in this subsection are not applicable and should be skipped. The following script creates and runs a function called f_ipv6_chk that may be used to determine if IPv6 has been disabled on the system: #!/usr/bin/env bash f_ipv6_chk() { a_output=() ! grep -Pqs -- '^\h*0\b' /sys/module/ipv6/parameters/disable && \ a_output+=(" - IPv6 is disabled") if sysctl net.ipv6.conf.all.disable_ipv6 | \ grep -Pqs -- "^\h*net\.ipv6\.conf\.all\.disable_ipv6\h*=\h*1\b" && \ sysctl net.ipv6.conf.default.disable_ipv6 | \ grep -Pqs -- "^\h*net\.ipv6\.conf\.default\.disable_ipv6\h*=\h*1\b"; then [ "${#a_output[@]}" -le 0 ] && a_output+=(" - IPv6 is disabled") fi [ "${#a_output[@]}" -le 0 ] && a_output+=(" - IPv6 is not disabled") printf '%s\n' "" "${a_output[@]}" "" } f_ipv6_chk Page 430 Internal Only - General 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The net.ipv6.conf.all.forwarding flag tells the system whether it can forward IPv6 packets or not. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Setting net.ipv6.conf.all.forwarding to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will not be able to forward IPv6 packets. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.forwarding is set to 0. 1. Run the following command to verify net.ipv6.conf.all.forwarding is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.forwarding Verify output is: net.ipv6.conf.all.forwarding = 0 2. Run the following script to verify net.ipv6.conf.all.forwarding = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.all.forwarding: Page 431 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.all.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 432 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.all.forwarding lines that are not net.ipv6.conf.all.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 433 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.forwarding = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.all.forwarding = 0 References: 1. CI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040260 | RULE ID: SV-230540r1017302 | CAT II 5. STIG ID: OL08-00-040260 | RULE ID: SV-248883r991589 | CAT II 6. STIG ID: RHEL-09-254025 | RULE ID: SV-257974r991589 | CAT II 7. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 8. STIG ID: OL09-00-006043 | RULE ID: SV-271880r1092352 | CAT II 9. STIG ID: SLES-15-040381 | RULE ID: SV-235025r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 434 Internal Only - General 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The net.ipv6.conf.all.forwarding flag tells the system whether it can forward IPv6 on the default or newly added network interface. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. Impact: IP forwarding is required on systems configured to act as a router. If these parameters are disabled, the system will not be able to perform as a router. Many Cloud Service Provider (CSP) hosted systems require IP forwarding to be enabled. If the system is running on a CSP platform, this requirement should be reviewed before disabling IP forwarding. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.forwarding is set to 0. 1. Run the following command to verify net.ipv6.conf.default.forwarding is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.forwarding Verify output is: net.ipv6.conf.default.forwarding = 0 2. Run the following script to verify net.ipv6.conf.default.forwarding = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.default.forwarding: Page 435 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.forwarding" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.default.forwarding = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 436 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.default.forwarding lines that are not net.ipv6.conf.default.forwarding=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.forwarding" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 437 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.forwarding = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.forwarding = 0" >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.default.forwarding = 0 References: 1. CI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: ALMA-09-019160 | RULE ID: SV-269249r1050131 | CAT II 5. STIG ID: SLES-15-040382 | RULE ID: SV-235026r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 438 Internal Only - General 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv6.conf.all.accept_redirects controls accepting of all IPv6 ICMP redirected packets on all interfaces. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv6.conf.all.accept_redirects to 0, the system will not accept any IPv6 ICMP redirect messages, and therefore, won't allow outsiders to update the system's routing tables. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_redirects is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_redirects Verify output is: net.ipv6.conf.all.accept_redirects = 0 2. Run the following script to verify net.ipv6.conf.all.accept_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.all.accept_redirects: Page 439 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.all.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 440 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.all.accept_redirects lines that are not net.ipv6.conf.all.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 441 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.all.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040280 | RULE ID: SV-230544r1017306 | CAT II 5. STIG ID: OL08-00-040280 | RULE ID: SV-248888r991589 | CAT II 6. STIG ID: RHEL-09-254015 | RULE ID: SV-257972r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006041 | RULE ID: SV-271878r1092346 | CAT II 9. STIG ID: SLES-15-040341 | RULE ID: SV-235020r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 442 Internal Only - General 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. net.ipv6.conf.default.accept_redirects controls accepting of all IPv6 ICMP redirected packets on a newly added network interface. Note: If IPv6 has been disabled, or this system is a router, this recommendation is not applicable. Rationale: ICMP redirect messages are packets that convey routing information and tell your host (acting as a router) to send packets via an alternate path. It is a way of allowing an outside routing device to update your system routing tables. By setting net.ipv6.conf.default.accept_redirects to 0, the system will not accept IPv6 ICMP redirect messages on a newly added network interface. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_redirects is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_redirects is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_redirects Verify output is: net.ipv6.conf.default.accept_redirects = 0 2. Run the following script to verify net.ipv6.conf.default.accept_redirects = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.default.accept_redirects: Page 443 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_redirects" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.default.accept_redirects = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 444 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.default.accept_redirects lines that are not net.ipv6.conf.default.accept_redirects=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_redirects" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 445 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.accept_redirects = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_redirects = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.default.accept_redirects = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040210 | RULE ID: SV-230535r1017297 | CAT II 5. STIG ID: OL08-00-040210 | RULE ID: SV-248876r991589 | CAT II 6. STIG ID: RHEL-09-254035 | RULE ID: SV-257976r991589 | CAT II 7. STIG ID: ALMA-09-018610 | RULE ID: SV-269244r1050126 | CAT II 8. STIG ID: OL09-00-006045 | RULE ID: SV-271882r1092358 | CAT II 9. STIG ID: SLES-15-040350 | RULE ID: SV-235021r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 446 Internal Only - General 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv6.conf.all.accept_source_route controls accepting of all IPv6 packets with the SSR or LSR option set on all interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. Note: If IPv6 has been disabled this recommendation is not applicable. Rationale: Setting net.ipv6.conf.all.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_source_route is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_source_route Verify output is: net.ipv6.conf.all.accept_source_route = 0 Page 447 Internal Only - General 2. Run the following script to verify net.ipv6.conf.all.accept_source_route = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.all.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.all.accept_source_route = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. • SYSTEM FILE PRECEDENCE Page 448 Internal Only - General o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.all.accept_source_route lines that are not net.ipv6.conf.all.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 449 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.all.accept_source_route = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040240 | RULE ID: SV-230538r1017300 | CAT II 5. STIG ID: OL08-00-040240 | RULE ID: SV-248880r991589 | CAT II 6. STIG ID: RHEL-09-254020 | RULE ID: SV-257973r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006042 | RULE ID: SV-271879r1092349 | CAT II 9. STIG ID: SLES-15-040310 | RULE ID: SV-235015r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 450 Internal Only - General 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The accept_source_route option causes network interfaces to accept packets with the Strict Source Route (SSR) or Loose Source Routing (LSR) option set. net.ipv6.conf.default.accept_source_route controls accepting of all IPv6 packets with the SSR or LSR option set on newly added network interfaces. In networking, source routing allows a sender to partially or fully specify the route packets take through a network. In contrast, non-source routed packets travel a path determined by routers in the network. In some cases, systems may not be routable or reachable from some locations (e.g. private addresses vs. Internet routable), and so source routed packets would need to be used. Note: If IPv6 has been disabled this recommendation is not applicable. Rationale: Setting net.ipv6.conf.default.accept_source_route to 0 disables the system from accepting source routed packets. Assume this system was capable of routing packets to Internet routable addresses on one interface and private addresses on another interface. Assume that the private addresses were not routable to the Internet routable addresses and vice versa. Under normal routing circumstances, an attacker from the Internet routable addresses could not use the system as a way to reach the private address systems. If, however, source routed packets were allowed, they could be used to gain access to the private address systems as the route could be specified, rather than rely on routing protocols that did not allow this routing. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_source_route is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_source_route is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_source_route Verify output is: net.ipv6.conf.default.accept_source_route = 0 Page 451 Internal Only - General 2. Run the following script to verify net.ipv6.conf.default.accept_source_route = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.default.accept_source_route: #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_source_route" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.default.accept_source_route = 0" is set in: "/etc/sysctl.d/60-ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 452 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.default.accept_source_route lines that are not net.ipv6.conf.default.accept_source_route=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_source_route" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 453 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.accept_source_route = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_source_route = 0" \ >> /etc/sysctl.d/60-ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.default.accept_source_route = 0 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040250 | RULE ID: SV-230539r1017301 | CAT II 5. STIG ID: OL08-00-040250 | RULE ID: SV-248882r991589 | CAT II 6. STIG ID: RHEL-09-254040 | RULE ID: SV-257977r991589 | CAT II 7. STIG ID: ALMA-09-020260 | RULE ID: SV-269259r1050141 | CAT II 8. STIG ID: OL09-00-006046 | RULE ID: SV-271883r1092361 | CAT II 9. STIG ID: SLES-15-040321 | RULE ID: SV-235017r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 454 Internal Only - General 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Routers periodically multicast Router Advertisement messages to announce their availability and convey information to neighboring nodes that enable them to be automatically configured on the network. net.ipv6.conf.all.accept_ra controls accepting any IPv6 RA messages on any network device. Note: If IPv6 has been disabled, this recommendation is not applicable. Rationale: It is recommended that systems do not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.all.accept_ra is set to 0. 1. Run the following command to verify net.ipv6.conf.all.accept_ra is set to 0 in the running configuration: # sysctl net.ipv6.conf.all.accept_ra Verify output is: net.ipv6.conf.all.accept_ra = 0 2. Run the following script to verify net.ipv6.conf.all.accept_ra = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.all.accept_ra: Page 455 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.all.accept_ra" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.all.accept_ra = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 456 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.all.accept_ra lines that are not net.ipv6.conf.all.accept_ra=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.all.accept_ra" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 457 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.all.accept_ra = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.all.accept_ra = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.all.accept_ra = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040261 | RULE ID: SV-230541r1017303 | CAT II 5. STIG ID: OL08-00-040261 | RULE ID: SV-248884r991589 | CAT II 6. STIG ID: RHEL-09-254010 | RULE ID: SV-257971r991589 | CAT II 7. STIG ID: ALMA-09-018500 | RULE ID: SV-269243r1050125 | CAT II 8. STIG ID: OL09-00-006040 | RULE ID: SV-271877r1092343 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 458 Internal Only - General 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Routers periodically Multicast Router Advertisement (RA) messages to announce their availability and convey information to neighboring nodes that enable them to be automatically configured on the network. net.ipv6.conf.default.accept_ra controls accepting IPv6 RA messages on newly added network devices. Note: If IPv6 has been disabled, this recommendation is not applicable. Rationale: It is recommended that systems do not accept router advertisements as they could be tricked into routing traffic to compromised machines. Setting hard routes within the system (usually a single default route to a trusted router) protects the system from bad routes. Audit: - IF IPv6 is enabled on the system - Verify net.ipv6.conf.default.accept_ra is set to 0. 1. Run the following command to verify net.ipv6.conf.default.accept_ra is set to 0 in the running configuration: # sysctl net.ipv6.conf.default.accept_ra Verify output is: net.ipv6.conf.default.accept_ra = 0 2. Run the following script to verify net.ipv6.conf.default.accept_ra = 0 is set in a file being used by systemd sysctl to configure net.ipv6.conf.default.accept_ra: Page 459 Internal Only - General #!/usr/bin/env bash { l_parameter_name="net.ipv6.conf.default.accept_ra" l_grep="${l_parameter_name//./(\\.|\\/)}" a_output=() a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do l_opt="$(grep -Poi '^\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_parameter_name = $l_option_value\" is set in:" \ " \"$l_file\"") done [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Example output: - "net.ipv6.conf.default.accept_ra = 0" is set in: "/etc/sysctl.d/60- ipv6_sysctl.conf" Note: • This script looks at all files used by systemd sysctl. • More information about these files and their location is available in the section overview. • If multiple lines are returned: o The first line includes the value being used by systemd sysctl. If this is a correct value, this is considered a passing state. If the file listed is not in the /etc/sysctl.d/ directory, it is highly recommended to follow the remediation procedure to create a .conf file in the /etc/sysctl.d/ directory with the correct setting to prevent a potential change due to an update to the system. o Any files in the /etc/sysctl.d/ directory that include an incorrect value should be modified to comment out or change the incorrect value to minimize the potential of the incorrect value being used by systemd sysctl due to system configuration changes. Page 460 Internal Only - General • SYSTEM FILE PRECEDENCE o When using the --system option, sysctl will read files from directories in the following list in given order from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf o All configuration files are sorted in lexicographic order, regardless of the directory they reside in. Configuration files can either be completely replaced (by having a new configuration file with the same name in a directory of higher priority) or partially replaced (by having a configuration file that is ordered later)-- Remediation: 1. Review all files being used by systemd sysctl and comment out or remove all net.ipv6.conf.default.accept_ra lines that are not net.ipv6.conf.default.accept_ra=0. Example script: #!/usr/bin/env bash { l_option="net.ipv6.conf.default.accept_ra" l_value="0" l_grep="${l_option//./(\\.|\\/)}" a_files=() l_systemdsysctl="$(readlink -e /lib/systemd/systemd-sysctl \ || readlink -e /usr/lib/systemd/systemd-sysctl)" l_ufw_file="$([ -f /etc/default/ufw ] && \ awk -F= '/^\s*IPT_SYSCTL=/ {print $2}' /etc/default/ufw)" [ -f "$(readlink -e "$l_ufw_file")" ] && \ a_files+=("$l_ufw_file"); a_files+=("/etc/sysctl.conf") while IFS= read -r l_fname; do l_file="$(readlink -e "${l_fname//# /}")" [ -n "$l_file" ] && ! grep -Psiq -- '(^|\h+)'"$l_file"'\b' \ <<< "${a_files[*]}" && a_files+=("$l_file") done < <("$l_systemdsysctl" --cat-config | tac | \ grep -Pio -- '^\h*#\h*\/[^#\n\r\h]+\.conf\b') for l_file in "${a_files[@]}"; do grep -Poi -- '\h*'"$l_grep"'\h*=\h*\H+\b' "$l_file" \ | grep -Pivq -- '^\h*'"$l_grep"'\h*=\h*'"$l_value"'\b' && \ sed -ri '/^\s*'"$l_grep"'\s*=\s*(1[0-9]*)/s/^/# /' "$l_file" done } Page 461 Internal Only - General 2. Create or edit a file in the /etc/sysctl.d/ directory ending in .confand edit or add the following line: net.ipv6.conf.default.accept_ra = 0 Example: # [ ! -d "/etc/sysctl.d/" ] && mkdir -p /etc/sysctl.d/ # printf '%s\n' "" "net.ipv6.conf.default.accept_ra = 0" >> /etc/sysctl.d/60- ipv6_sysctl.conf Note: If the UFW file was the first file listed in the audit, the entry will be commented out as part of the first step, however updating Uncomplicated Firewall (UFW) may update this change. In this case the updated entry will supersede the entry being created as part of this step. 3. Run the following command to load all sysctl configuration filles: # sysctl --system Default Value: net.ipv6.conf.default.accept_ra = 1 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-040262 | RULE ID: SV-230542r1017304 | CAT II 5. STIG ID: OL08-00-040262 | RULE ID: SV-248885r991589 | CAT II 6. STIG ID: RHEL-09-254030 | RULE ID: SV-257975r991589 | CAT II 7. STIG ID: ALMA-09-018500 | RULE ID: SV-269243r1050125 | CAT II 8. STIG ID: OL09-00-006044 | RULE ID: SV-271881r1092355 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 462 Internal Only - General 4 Host Based Firewall A firewall is a set of rules. When a data packet moves into or out of a protected network space, its contents (in particular, information about its origin, target, and the protocol it plans to use) are tested against the firewall rules to see if it should be allowed through. To provide a Host Based Firewall, the Linux kernel includes support for NFTables. NFTables is subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames. NFTables replaces parts of Netfilter, while keeping and reusing most of it. NFTables utilizes the building blocks of the Netfilter infrastructure, such as the existing hooks into the networking stack, connection tracking system, userspace queueing component, and logging subsystem. In order to configure firewall rules for NFTables, a firewall utility needs to be installed. Guidance has been included for Uncomplicated Firewall (UFW) which provides firewall features by acting as a front-end for the Linux kernel's netfilter framework via the NFTables backend, acting as an alternative to the nft command line program. UFW supports both IPv4 and IPv6 networks. Important: This Benchmark includes guidance for configuring NFTables though the UFW front end utility. If your organization is using a different Host Based Firewall, or a different utility to configure the Host Based Firewall, we recommend verifying that your site's configuration meets the Recommendations in this section, otherwise this section may be skipped. Note: • Only one method should be used to configure a firewall on the system. Use of more than one method could produce unexpected results. • NFTables is the default packet filtering framework. Though IPTables is still supported, this support is done indirectly through UFW's ability to translate IPTables commands to NFTables. • This section is intended only to ensure the resulting firewall rules are in place. Page 463 Internal Only - General 4.1 Configure Uncomplicated Firewall In order to configure durable firewall rules a firewall utility needs to be installed. Uncomplicated Firewall (UFW) is the recommended utility and is used in guidance provided in the following recommendations. UFW is a user-friendly frontend firewall utility. It uses configurable default policies, and allows administrators to create specific rules to permit or deny connections based on applications, ports, or IP addresses. You can enable the firewall, view its status, and manage rules using simple command-line tools to secure your system. Warning: Configuration of a live systems firewall directly over a remote connection will often result in being locked out. It is advised to have a known good firewall configuration set to run on boot and to configure an entire firewall structure in a script that is then run and tested before saving to boot. Page 464 Internal Only - General 4.1.1 Ensure ufw is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Uncomplicated Firewall (ufw) is a frontend for iptables and is particularly well-suited for host-based firewalls. ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall Rationale: UFW acts as a frontend for both iptables and nftables and can use either as its backend, though the specific backend depends on the Linux distribution and system configuration. You can enable the firewall, view its status, and manage rules using simple command- line tools to secure your system. Impact: Changing firewall settings while connected over the network can result in being locked out of the system. Audit: Run the following command to verify that Uncomplicated Firewall (UFW) is installed: # dpkg-query -s ufw &>/dev/null && echo "ufw is installed" ufw is installed Remediation: Run the following command to install Uncomplicated Firewall (UFW): # apt install ufw References: 1. CCI-002314 2. NIST SP 800-53 :: AC-17 (1) 3. STIG ID: UBTU-22-251010 | Rule ID: SV-260514r958672 | CAT II 4. STIG ID: UBTU-24-100300 | Rule ID: SV-270654r1067143 | CAT II Page 465 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 466 Internal Only - General 4.1.2 Ensure ufw service is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The service, ufw.service, manages UFW. This service is responsible for applying and maintaining firewall rules, controlling which network traffic is allowed in and out of the system. Note: • When running ufw enable or starting ufw.service, ufw will flush its chains. This is required so ufw can maintain a consistent state, but it may drop existing connections, eg ssh. ufw does support adding rules before enabling the firewall. • Once ufw is 'enabled', ufw will not flush the chains when adding or removing rules (but will when modifying a rule or changing the default policy) • By default ufw will prompt when enabling the firewall while running under ssh. This can be disabled by using ufw --force enable Warning: If a rule for openSSH server does not exist, and openSSH is used to administer the host, the ability to administer and/or connect to the host may be lost. Example command to create a rule to allow ssh: # ufw allow proto tcp from any to any port 22 This rule will allow connection to the ssh server from any location. It is highly recommended that this rule be modified to restrict ssh access to only required hosts and to follow local site policy. • The rules will still be flushed, but the ssh port will be open after enabling the firewall. Please note that once ufw is 'enabled', ufw will not flush the chains when adding or removing rules (but will when modifying a rule or changing the default policy) • By default, ufw will prompt when enabling the firewall while running under ssh. This can be disabled by using ufw --force enable Rationale: The ufw service must be enabled and running in order for ufw to protect the system Impact: Changing firewall settings while connected over network can result in being locked out of the system. Page 467 Internal Only - General Audit: Run the following command to verify ufw.service is enabled: # systemctl is-enabled ufw.service enabled Run the following command to verify ufw.service is active: # systemctl is-active ufw.service active Run the following command to verify ufw is active # ufw status Status: active Remediation: Run the following command to unmask the ufw.service: # systemctl unmask ufw.service Run the following command to enable and start the ufw.service: # systemctl --now enable ufw.service active Run the following command to enable ufw: # ufw enable Default Value: Inactive References: 1. CCI-002314 2. NIST SP 800-53 :: AC-17 (1) 3. STIG ID: UBTU-20-010434 | Rule ID: SV-238355r958672 | CAT II 4. STIG ID: UBTU-22-251015 | Rule ID: SV-260515r958672 | CAT II 5. STIG ID: UBTU-24-100310 | Rule ID: SV-270655r1067145 | CAT II 6. http://manpages.ubuntu.com/manpages/precise/en/man8/ufw.8.html Page 468 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 469 Internal Only - General 4.1.3 Ensure ufw incoming default is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The default policy for incoming traffic determines if connections attempting to reach your server from external sources will be allowed without requiring specific UFW rules. Rationale: With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to allow list acceptable usage than to deny list unacceptable usage. Impact: Any port or protocol without a explicit allow before the default deny will be blocked. A deny policy silently drops packs causing an eventual time out with no response while a 'reject' policy sends an immediate and explicit "connection refused" or "destination unreachable" message in response. The following is and example of a command to create a rule to allow connection to the ssh server on the host. This rule should be considered before applying the default deny. Example: # ufw allow ssh Audit: Run the following command to verify that the default policy for incoming is deny or reject: # ufw status verbose | awk -F',' '$1~/Default/ {print $1}' Example output: Default: deny (incoming) Remediation: Run the following command to set the default for incoming to deny: # ufw default deny incoming Warning: Any port or protocol without a explicit allow before the default deny will be blocked. References: 1. NIST SP 800-53 Rev. 5: SC-7 Page 470 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 471 Internal Only - General 4.1.4 Ensure ufw outgoing default is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The default policy for outgoing traffic determines if applications and services running on your server can initiate connections to external networks without requiring specific UFW rules. Rationale: With a default deny outgoing policy the firewall will deny ALL outgoing traffic and is a highly restrictive policy that requires the addition of specific allow rules. Impact: Any port and protocol not explicitly allowed will be blocked. The following rules are an example of some outgoing allow rules that should be considered before applying this default deny. ufw allow out http ufw allow out https ufw allow out ntp # Network Time Protocol ufw allow out to any port 53 # DNS ufw allow out to any port 853 # DNS over TLS ufw logging on Audit: Run the following command and verify that the default policy for outgoing is deny or reject: # ufw status verbose | awk -F',' '$1~/Default/ {print $2}' Example output: deny (outgoing) Remediation: Run the following command to set the default for outgoing to deny: # ufw default deny outgoing Warning: Any port or protocol without a explicit allow before the default deny will be blocked. Default Value: allow (outgoing) Page 472 Internal Only - General References: 1. CCI-000382 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (iii) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. Page 473 Internal Only - General 4.1.5 Ensure ufw routed default is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The default policy for routed traffic determines if UFW forwards traffic between different network interfaces without requiring specific UFW rules. Rationale: A default deny policy ensures that UFW does not forward traffic between different network interfaces by default. This reduces the risk from unwanted or malicious routed traffic. Impact: Any port and protocol will be prevented for being routed. Audit: Run the following command and verify that the default policy for routed is disabled or deny: # ufw status verbose | awk -F',' '$1="Default"{print $3}' Example output: disabled (routed) Important: Any port and protocol will be prevented for being routed. Remediation: Run the following command to set the default policy for routed to deny: # ufw default deny routed Default Value: disabled References: 1. CCI-000382 2. NIST SP 800-53 :: CM-7 3. NIST SP 800-53A :: CM-7.1 (iii) Page 474 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.4 Implement and Manage a Firewall on Servers v8 Implement and manage a firewall on servers, where supported. Example implementations include a virtual firewall, operating system firewall, or a third- ● ● ● party firewall agent. 4.5 Implement and Manage a Firewall on End-User Devices v8 Implement and manage a host-based firewall or port-filtering tool on end-user ● ● ● devices, with a default-deny rule that drops all traffic except those services and ports that are explicitly allowed. 9.4 Apply Host-based Firewalls or Port Filtering v7 Apply host-based firewalls or port filtering tools on end systems, with a default-deny rule that drops all traffic except those services and ports that are ● ● ● explicitly allowed. 5 Access Control Page 475 Internal Only - General 5.1 Configure SSH Server Secure Shell (SSH) is a secure, encrypted replacement for common login services such as telnet, ftp, rlogin, rsh, and rcp. It is strongly recommended that sites abandon older clear-text login protocols and use SSH to prevent session hijacking and sniffing of sensitive data off the network. The recommendations in this section only apply if the SSH daemon is installed on the system, if remote access is not required the SSH daemon can be removed and this section skipped. sshd_config: • The openSSH daemon configuration directives, Include and Match, may cause the audits in this section's recommendations to report incorrectly. It is recommended that these options only be used if they're needed and fully understood. If these options are configured in accordance with local site policy, they should be accounted for when following the recommendations in this section. • The default Include location is the /etc/ssh/sshd_config.d directory. This default has been accounted for in this section. If a file has an additional Include that isn't this default location, the files should be reviewed to verify that the recommended setting is not being over-ridden. • The audits of the running configuration in this section are run in the context of the root user, the local host name, and the local host's IP address. If a Match block exists that matches one of these criteria, the output of the audit will be from the match block. The respective matched criteria should be replaced with a non- matching substitution. • Include: o Include the specified configuration file(s). o Multiple pathnames may be specified and each pathname may contain glob(7) wildcards that will be expanded and processed in lexical order. o Files without absolute paths are assumed to be in /etc/ssh/. o An Include directive may appear inside a Match block to perform conditional inclusion. • Match: o Introduces a conditional block. If all of the criteria on the Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another Match line or the end of the file. If a keyword appears in multiple Match blocks that are satisfied, only the first instance of the keyword is applied. o The arguments to Match are one or more criteria-pattern pairs or the single token All which matches all criteria. The available criteria are User, Group, Host, LocalAddress, LocalPort, and Address. o The match patterns may consist of single entries or comma-separated lists and may use the wildcard and negation operators described in the PATTERNS section of ssh_config(5). Page 476 Internal Only - General o The patterns in an Address criteria may additionally contain addresses to match in CIDR address/masklen format, such as 192.0.2.0/24 or 2001:db8::/32. Note that the mask length provided must be consistent with the address - it is an error to specify a mask length that is too long for the address or one with bits set in this host portion of the address. For example, 192.0.2.0/33 and 192.0.2.0/8, respectively. o Only a subset of keywords may be used on the lines following a Match keyword. Available keywords are available in the ssh_config man page. • Once all configuration changes have been made to /etc/ssh/sshd_config or any included configuration files, the sshd configuration must be reloaded Command to re-load the SSH daemon configuration: # systemctl reload-or-restart sshd sshd command: • -T - Extended test mode. Check the validity of the configuration file, output the effective configuration to stdout and then exit. Optionally, Match rules may be applied by specifying the connection parameters using one or more -C options. • -C - connection_spec. Specify the connection parameters to use for the -T extended test mode. If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr, user, host, laddr, lport, and rdomain and correspond to source address, user, resolved source host name, local address, local port number and routing domain respectively. Page 477 Internal Only - General 5.1.1 Ensure access to /etc/ssh/sshd_config is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The file /etc/ssh/sshd_config, and files ending in .conf in the /etc/ssh/sshd_config.d directory, contain configuration specifications for sshd. Rationale: Configuration specifications for sshd need to be protected from unauthorized changes by non-privileged users. Audit: Run the following script and verify /etc/ssh/sshd_config and files ending in .conf in the /etc/ssh/sshd_config.d directory are: • Mode 0600 or more restrictive • Owned by the root user • Group owned by the group root. Page 478 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=() perm_mask='0177' && maxperm="$( printf '%o' $(( 0777 & ~$perm_mask)) )" f_sshd_files_chk() { while IFS=: read -r l_mode l_user l_group; do a_out2=() [ $(( $l_mode & $perm_mask )) -gt 0 ] && a_out2+=(" Is mode: \"$l_mode\"" \ " should be mode: \"$maxperm\" or more restrictive") [ "$l_user" != "root" ] && a_out2+=(" Is owned by \"$l_user\" should be owned by \"root\"") [ "$l_group" != "root" ] && a_out2+=(" Is group owned by \"$l_user\" should be group owned by \"root\"") if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=(" - File: \"$l_file\":" "${a_out2[@]}") else a_output+=(" - File: \"$l_file\":" " Correct: mode ($l_mode), owner ($l_user)" \ " and group owner ($l_group) configured") fi done < <(stat -Lc '%#a:%U:%G' "$l_file") } [ -e "/etc/ssh/sshd_config" ] && l_file="/etc/ssh/sshd_config" && f_sshd_files_chk while IFS= read -r -d $'\0' l_file; do [ -e "$l_file" ] && f_sshd_files_chk done < <(find /etc/ssh/sshd_config.d -type f -name '*.conf' \( -perm /077 -o ! -user root -o ! -group root \) -print0 2>/dev/null) if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } - IF - other locations are listed in an Include statement, *.conf files in these locations should also be checked. Page 479 Internal Only - General Remediation: Run the following script to set ownership and permissions on /etc/ssh/sshd_config and files ending in .conf in the /etc/ssh/sshd_config.d directory: #!/usr/bin/env bash { chmod u-x,og-rwx /etc/ssh/sshd_config chown root:root /etc/ssh/sshd_config while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then chmod u-x,og-rwx "$l_file" chown root:root "$l_file" fi done < <(find /etc/ssh/sshd_config.d -type f -print0 2>/dev/null) } - IF - other locations are listed in an Include statement, *.conf files in these locations access should also be modified. Default Value: Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 480 Internal Only - General 5.1.2 Ensure access to SSH private host key files is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An SSH private key is one of two files used in SSH public key authentication. In this authentication method, the possession of the private key is proof of identity. Only a private key that corresponds to a public key will be able to authenticate successfully. The private keys need to be stored and handled carefully, and no copies of the private key should be distributed. Rationale: If an unauthorized user obtains the private SSH host key file, the host could be impersonated Audit: Run the following script to verify SSH private host key files are: • Mode 0600 or more restrictive. • Owned by the root user. • Group owned by the group root. Page 481 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() l_pmask="0177" l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" f_file_chk() { while IFS=: read -r l_fmode l_fowner l_fgroup; do a_out2=() if [ $(( $l_fmode & $l_pmask )) -gt 0 ]; then a_out2+=(" - mode: \"$l_fmode\"" \ " should be mode: \"$l_maxperm\" or more restrictive") fi if [ "$l_fowner" != "root" ]; then a_out2+=(" - owned by: \"$l_fowner\"" \ " should be owned by \"root\"") fi if [ "$l_fgroup" != "root" ]; then a_out2+=(" - group owned by: \"$l_fgroup\"" \ " should be group owned by group: \"root\"") fi if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=(" - File: \"$l_file\"" "${a_out2[@]}") else a_output+=(" - File: \"$l_file\" Correct:" \ " - mode: \"$l_fmode\"" \ " - owner: \"$l_fowner\"" " - group owner: \"$l_fgroup\"") fi done < <(stat -Lc '%#a:%U:%G' "$l_file") } while IFS= read -r -d $'\0' l_file; do if ssh-keygen -lf &>/dev/null "$l_file"; then file "$l_file" | \ grep -Piq -- '\bopenssh\h+([^#\n\r]+\h+)?private\h+key\b' && f_file_chk fi done < <(find -L /etc/ssh -xdev -type f -print0 2>/dev/null) if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" \ " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && \ printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } Page 482 Internal Only - General Remediation: Run the following script to set mode, ownership, and group on the private SSH host key files: #!/usr/bin/env bash { a_output2=() l_pmask="0177" l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" f_file_access_fix() { while IFS=: read -r l_file_mode l_file_owner l_file_group; do a_out2=() if [ $(( $l_file_mode & $l_pmask )) -gt 0 ]; then a_out2+=("" " Mode: \"$l_file_mode\"" \ " should be mode: \"$l_maxperm\" or more restrictive" \ " updating to mode: \"$l_maxperm\"") chmod u-x,go-rwx "$l_file" fi if [ "$l_file_owner" != "root" ]; then a_out2+=("" " Owned by: \"$l_file_owner\"" \ " should be owned by \"root\"" \ " Changing ownership to \"root\"") chown root "$l_file" fi if [ "$l_file_group" != "root" ]; then a_out2+=("" " Owned by group \"$l_file_group\"" \ " should be group owned by: \"root\"" \ " Changing group ownership to group: \"root\"") chgrp root "$l_file" fi if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=("" " - File: \"$l_file\"" "${a_out2[@]}") fi done < <(stat -Lc '%#a:%U:%G' "$l_file") } while IFS= read -r -d $'\0' l_file; do if ssh-keygen -lf &>/dev/null "$l_file"; then file "$l_file" | grep -Piq -- \ '\bopenssh\h+([^#\n\r]+\h+)?private\h+key\b' && f_file_access_fix fi done < <(find -L /etc/ssh -xdev -type f -print0 2>/dev/null) if [ "${#a_output2[@]}" -le "0" ]; then printf '%s\n' "" " - No access changes required" "" else printf '%s\n' "" " - Remediation results:" "${a_output2[@]}" "" fi } Page 483 Internal Only - General References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-010490 | RULE ID: SV-230287r1017098 | CAT II 5. STIG ID: RHEL-09-255120 | RULE ID: SV-258000r1045063 | CAT II 6. STIG ID: ALMA-09-020920 | RULE ID: SV-269265r1050147 | CAT II 7. STIG ID: SLES-15-040250 | RULE ID: SV-235009r991589 | CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 484 Internal Only - General 5.1.3 Ensure access to SSH public host key files is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An SSH public key is one of two files used in SSH public key authentication. In this authentication method, a public key is a key that can be used for verifying digital signatures generated using a corresponding private key. Only a public key that corresponds to a private key will be able to authenticate successfully. Rationale: If a public host key file is modified by an unauthorized user, the SSH service may be compromised. Audit: Run the following command and verify Access does not grant write or execute permissions to group or other for all returned files: Run the following script to verify SSH public host key files are mode 0644 or more restrictive, owned by the root user, and owned by the root group: Page 485 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=() l_pmask="0133"; l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" f_file_chk() { while IFS=: read -r l_file_mode l_file_owner l_file_group; do a_out2=() if [ $(( $l_file_mode & $l_pmask )) -gt 0 ]; then a_out2+=(" Mode: \"$l_file_mode\" should be mode: \"$l_maxperm\" or more restrictive") fi if [ "$l_file_owner" != "root" ]; then a_out2+=(" Owned by: \"$l_file_owner\" should be owned by: \"root\"") fi if [ "$l_file_group" != "root" ]; then a_out2+=(" Owned by group \"$l_file_group\" should be group owned by group: \"root\"") fi if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=(" - File: \"$l_file\"" "${a_out2[@]}") else a_output+=(" - File: \"$l_file\"" \ " Correct: mode: \"$l_file_mode\", owner: \"$l_file_owner\" and group owner: \"$l_file_group\" configured") fi done < <(stat -Lc '%#a:%U:%G' "$l_file") } while IFS= read -r -d $'\0' l_file; do if ssh-keygen -lf &>/dev/null "$l_file"; then file "$l_file" | grep -Piq -- '\bopenssh\h+([^#\n\r]+\h+)?public\h+key\b' && f_file_chk fi done < <(find -L /etc/ssh -xdev -type f -print0 2>/dev/null) if [ "${#a_output2[@]}" -le 0 ]; then [ "${#a_output[@]}" -le 0 ] && a_output+=(" - No openSSH public keys found") printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "" "- Correctly set:" "${a_output[@]}" "" fi } Page 486 Internal Only - General Remediation: Run the following script to set mode, ownership, and group on the public SSH host key files: #!/usr/bin/env bash { a_output=(); a_output2=() l_pmask="0133"; l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" f_file_access_fix() { while IFS=: read -r l_file_mode l_file_owner l_file_group; do a_out2=() [ $(( $l_file_mode & $l_pmask )) -gt 0 ] && \ a_out2+=(" Mode: \"$l_file_mode\" should be mode: \"$l_maxperm\" or more restrictive" \ " updating to mode: \"$l_maxperm\"") && chmod u-x,go-wx "$l_file" [ "$l_file_owner" != "root" ] && \ a_out2+=(" Owned by: \"$l_file_owner\" should be owned by \"root\"" \ " Changing ownership to \"root\"") && chown root "$l_file" [ "$l_file_group" != "root" ] && \ a_out2+=(" Owned by group \"$l_file_group\" should be group owned by: \"root\"" \ " Changing group ownership to \"root\"") && chgrp root "$l_file" if [ "${#a_out2[@]}" -gt "0" ]; then a_output2+=(" - File: \"$l_file\"" "${a_out2[@]}") else a_output+=(" - File: \"$l_file\"" \ " Correct: mode: \"$l_file_mode\", owner: \"$l_file_owner\", and group owner: \"$l_file_group\" configured") fi done < <(stat -Lc '%#a:%U:%G' "$l_file") } while IFS= read -r -d $'\0' l_file; do if ssh-keygen -lf &>/dev/null "$l_file"; then file "$l_file" | grep -Piq -- '\bopenssh\h+([^#\n\r]+\h+)?public\h+key\b' && f_file_access_fix fi done < <(find -L /etc/ssh -xdev -type f -print0 2>/dev/null) if [ "${#a_output2[@]}" -le "0" ]; then printf '%s\n' "" " - No access changes required" "" else printf '%s\n' " - Remediation results:" "${a_output2[@]}" "" fi } Default Value: 644 0/root 0/root Page 487 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 488 Internal Only - General 5.1.4 Ensure sshd access is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are several options available to limit which users and group can access the system via SSH. It is recommended that at least one of the following options be leveraged: • AllowUsers: o The AllowUsers variable gives the system administrator the option of allowing specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by only allowing the allowed users to log in from a particular host, the entry can be specified in the form of user@host. • AllowGroups: o The AllowGroups variable gives the system administrator the option of allowing specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable. • DenyUsers: o The DenyUsers variable gives the system administrator the option of denying specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by specifically denying a user's access from a particular host, the entry can be specified in the form of user@host. • DenyGroups: o The DenyGroups variable gives the system administrator the option of denying specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable. Rationale: Restricting which users can remotely access the system via SSH will help ensure that only authorized users access the system. Page 489 Internal Only - General Audit: Run the following command and verify the output: # sshd -T | grep -Pi -- '^\h*(allow|deny)(users|groups)\h+\H+' Verify that the output matches at least one of the following lines: allowusers -OR- allowgroups -OR- denyusers -OR- denygroups Review the list(s) to ensure included users and/or groups follow local site policy - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '^\h*(allow|deny)(users|groups)\h+\H+' Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain). Remediation: Edit the /etc/ssh/sshd_config file to set one or more of the parameters above any Include and Match set statements as follows: AllowUsers - AND/OR - AllowGroups Note: • First occurrence of a option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a .conf file in a Include directory. • Be advised that these options are "ANDed" together. If both AllowUsers and AllowGroups are set, connections will be limited to the list of users that are also a member of an allowed group. It is recommended that only one be set for clarity and ease of administration. • It is easier to manage an allow list than a deny list. In a deny list, you could potentially add a user or group and forget to add it to the deny list. Page 490 Internal Only - General Default Value: None References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: AC-3. MP-2 3. SSHD(8) 4. https://documentation.suse.com/en-us/sles/15-SP6/html/SLES-all/cha-ssh.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 491 Internal Only - General 5.1.5 Ensure sshd Banner is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The Banner parameter specifies a file whose contents must be sent to the remote user before authentication is permitted. By default, no banner is displayed. Rationale: Banners are used to warn connecting users of the particular site's policy regarding connection. Presenting a warning message prior to the normal user login may assist the prosecution of trespassers on the computer system. Audit: Run the following command to verify Banner is set: # sshd -T | grep -Pi -- '^banner\h+\/\H+' Example: banner /etc/issue.net - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '^banner\h+\/\H+' Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain). Run the following command and verify that the contents or the file being called by the Banner argument match site policy: # [ -e "$(sshd -T | awk '$1 == "banner" {print $2}')" ] && cat "$(sshd -T | awk '$1 == "banner" {print $2}')" Run the following command and verify no results are returned: # grep -Psi -- "(\\\v|\\\r|\\\m|\\\s|\b$(grep '^ID=' /etc/os-release | cut - d= -f2 | sed -e 's/"//g')\b)" "$(sshd -T | awk '$1 == "banner" {print $2}')" Page 492 Internal Only - General Remediation: Edit the /etc/ssh/sshd_config file to set the Banner parameter above any Include and Match entries as follows: Banner /etc/issue.net Note: First occurrence of a option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Edit the file being called by the Banner argument with the appropriate contents according to your site policy, remove any instances of \m , \r , \s , \v or references to the OS platform Example: # printf '%s\n' "Authorized users only. All activity may be monitored and reported." > "$(sshd -T | awk '$1 == "banner" {print $2}')" References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 493 Internal Only - General 5.1.6 Ensure sshd Ciphers are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: This variable limits the ciphers that SSH can use during communication. Notes: • Some organizations may have stricter requirements for approved ciphers. • Ensure that ciphers used are in compliance with site policy. • The only "strong" ciphers currently FIPS 140 compliant are: o aes256-gcm@openssh.com o aes128-gcm@openssh.com o aes256-ctr o aes192-ctr o aes128-ctr Rationale: Weak ciphers that are used for authentication to the cryptographic module cannot be relied upon to provide confidentiality or integrity, and system data may be compromised. • The Triple DES ciphers, as used in SSH, have a birthday bound of approximately four billion blocks, which makes it easier for remote attackers to obtain clear text data via a birthday attack against a long-duration encrypted session, aka a "Sweet32" attack. • Error handling in the SSH protocol; Client and Server, when using a block cipher algorithm in Cipher Block Chaining (CBC) mode, makes it easier for remote attackers to recover certain plain text data from an arbitrary block of cipher text in an SSH session via unknown vectors. Page 494 Internal Only - General Audit: Run the following command to verify none of the "weak" ciphers are being used: # sshd -T | grep -Pi -- '^ciphers\h+\"?([^#\n\r]+,)?((3des|blowfish|cast128|aes(128|192|256))- cbc|arcfour(128|256)?|rijndael-cbc@lysator\.liu\.se|chacha20- poly1305@openssh\.com)\b' - IF - a line is returned, review the list of ciphers. If the line includes chacha20- poly1305@openssh.com, review CVE-2023-48795 and verify the system has been patched. No ciphers in the list below should be returned as they're considered "weak": 3des-cbc aes128-cbc aes192-cbc aes256-cbc Remediation: Edit the /etc/ssh/sshd_config file and add/modify the Ciphers line to contain a comma separated list of the site unapproved (weak) Ciphers preceded with a - above any Include entries: Example: Ciphers -3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc,chacha20- poly1305@openssh.com - IF - CVE-2023-48795 has been addressed, and it meets local site policy, chacha20- poly1305@openssh.com may be removed from the list of excluded ciphers. Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: Ciphers chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128- gcm@openssh.com,aes256-gcm@openssh.com References: 1. https://nvd.nist.gov/vuln/detail/CVE-2023-48795 2. https://nvd.nist.gov/vuln/detail/CVE-2019-1543 3. https://nvd.nist.gov/vuln/detail/CVE-2016-2183 4. https://nvd.nist.gov/vuln/detail/CVE-2008-5161 5. https://www.openssh.com/txt/cbc.adv 6. https://www.openssh.com/txt/cbc.adv 7. SSHD_CONFIG(5) 8. NIST SP 800-53 Rev. 5: SC-8 Page 495 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 496 Internal Only - General 5.1.7 Ensure sshd ClientAliveInterval and ClientAliveCountMax are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Note: To clarify, the two settings described below are only meant for idle connections from a protocol perspective and are not meant to check if the user is active or not. An idle user does not mean an idle connection. SSH does not and never had, intentionally, the capability to drop idle users. In SSH versions before 8.2p1 there was a bug that caused these values to behave in such a manner that they were abused to disconnect idle users. This bug has been resolved in 8.2p1 and thus it can no longer be abused disconnect idle users. The two options ClientAliveInterval and ClientAliveCountMax control the timeout of SSH sessions. Taken directly from man 5 sshd_config: • ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. • ClientAliveCountMax Sets the number of client alive messages which may be sent without sshd(8) receiving any messages back from the client. If this threshold is reached while client alive messages are being sent, sshd will disconnect the client, terminating the session. It is important to note that the use of client alive messages is very different from TCPKeepAlive. The client alive messages are sent through the encrypted channel and therefore will not be spoofable. The TCP keepalive option en‐abled by TCPKeepAlive is spoofable. The client alive mechanism is valuable when the client or server depend on knowing when a connection has become unresponsive. The default value is 3. If ClientAliveInterval is set to 15, and ClientAliveCountMax is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds. Setting a zero ClientAliveCountMax disables connection termination. Page 497 Internal Only - General Rationale: In order to prevent resource exhaustion, appropriate values should be set for both ClientAliveInterval and ClientAliveCountMax. Specifically, looking at the source code, ClientAliveCountMax must be greater than zero in order to utilize the ability of SSH to drop idle connections. If connections are allowed to stay open indefinitely, this can potentially be used as a DDOS attack or simple resource exhaustion could occur over unreliable networks. The example set here is a 45 second timeout. Consult your site policy for network timeouts and apply as appropriate. Audit: Run the following command and verify ClientAliveInterval and ClientAliveCountMax are greater than zero: # sshd -T | grep -Pi -- '(clientaliveinterval|clientalivecountmax)' Example Output: clientaliveinterval 15 clientalivecountmax 3 - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep -Pi -- '(clientaliveinterval|clientalivecountmax)' Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain). Remediation: Edit the /etc/ssh/sshd_config file to set the ClientAliveInterval and ClientAliveCountMax parameters above any Include and Match entries according to site policy. Example: ClientAliveInterval 15 ClientAliveCountMax 3 Note: First occurrence of a option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Page 498 Internal Only - General Default Value: ClientAliveInterval 0 ClientAliveCountMax 3 References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Additional Information: https://bugzilla.redhat.com/show_bug.cgi?id=1873547 https://github.com/openssh/openssh-portable/blob/V_8_9/serverloop.c#L137 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 499 Internal Only - General 5.1.8 Ensure sshd DisableForwarding is enabled (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The DisableForwarding parameter disables all forwarding features, including X11, ssh-agent(1), TCP and StreamLocal. This option overrides all other forwarding-related options and may simplify restricted configurations. • X11Forwarding provides the ability to tunnel X11 traffic through the connection to enable remote graphic connections. • ssh-agent is a program to hold private keys used for public key authentication. Through use of environment variables the agent can be located and automatically used for authentication when logging in to other machines using ssh. • SSH port forwarding is a mechanism in SSH for tunneling application ports from the client to the server, or servers to clients. It can be used for adding encryption to legacy applications, going through firewalls, and some system administrators and IT professionals use it for opening backdoors into the internal network from their home machines. Rationale: Disable X11 forwarding unless there is an operational requirement to use X11 applications directly. There is a small risk that the remote X11 servers of users who are logged in via SSH with X11 forwarding could be compromised by other users on the X11 server. Note that even if X11 forwarding is disabled, users can always install their own forwarders. anyone with root privilege on the the intermediate server can make free use of ssh- agent to authenticate them to other servers Leaving port forwarding enabled can expose the organization to security risks and backdoors. SSH connections are protected with strong encryption. This makes their contents invisible to most deployed network monitoring and traffic filtering solutions. This invisibility carries considerable risk potential if it is used for malicious purposes such as data exfiltration. Cybercriminals or malware could exploit SSH to hide their unauthorized communications, or to exfiltrate stolen data from the target network. Impact: SSH tunnels are widely used in many corporate environments. In some environments the applications themselves may have very limited native support for security. By utilizing tunneling, compliance with SOX, HIPAA, PCI-DSS, and other standards can be achieved without having to modify the applications. Page 500 Internal Only - General Audit: Run the following command to verify DisableForwarding is set to yes: # sshd -T | grep disableforwarding disableforwarding yes - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep disableforwarding Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit the /etc/ssh/sshd_config file to set the DisableForwarding parameter to yes above any Include and Match entries as follows: DisableForwarding yes Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: disableforwarding no References: 1. sshd_config(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-7 Page 501 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 502 Internal Only - General 5.1.9 Ensure sshd GSSAPIAuthentication is disabled (Automated) Profile Applicability: • Level 1 - Workstation • Level 2 - Server Description: The GSSAPIAuthentication parameter specifies whether user authentication based on GSSAPI is allowed Rationale: Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, and should be disabled to reduce the attack surface of the system Audit: Run the following command to verify GSSAPIAuthentication is set to no: # sshd -T | grep gssapiauthentication gssapiauthentication no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep gssapiauthentication Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit the /etc/ssh/sshd_config file to set the GSSAPIAuthentication parameter to no above any Include and Match entries as follows: GSSAPIAuthentication no Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: GSSAPIAuthentication no Page 503 Internal Only - General References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 504 Internal Only - General 5.1.10 Ensure sshd HostbasedAuthentication is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The HostbasedAuthentication parameter specifies if authentication is allowed through trusted hosts via the user of .rhosts, or /etc/hosts.equiv, along with successful public key client host authentication. Rationale: Even though the .rhosts files are ineffective if support is disabled in /etc/pam.conf, disabling the ability to use .rhosts files in SSH provides an additional layer of protection. Audit: Run the following command to verify HostbasedAuthentication is set to no: # sshd -T | grep hostbasedauthentication hostbasedauthentication no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep hostbasedauthentication Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit the /etc/ssh/sshd_config file to set the HostbasedAuthentication parameter to no above any Include and Match entries as follows: HostbasedAuthentication no Note: First occurrence of a option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Page 505 Internal Only - General Default Value: HostbasedAuthentication no References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 506 Internal Only - General 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The IgnoreRhosts parameter specifies that .rhosts and .shosts files will not be used in RhostsRSAAuthentication or HostbasedAuthentication. Rationale: Setting this parameter forces users to enter a password when authenticating with SSH. Audit: Run the following command to verify IgnoreRhosts is set to yes: # sshd -T | grep ignorerhosts ignorerhosts yes Remediation: Edit the /etc/ssh/sshd_config file to set the IgnoreRhosts parameter to yes above any Include entry as follows: IgnoreRhosts yes Note: First occurrence of a option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: IgnoreRhosts yes References: 1. SSHD_CONFIG(5) 2. SSHD(8) 3. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 Page 507 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 508 Internal Only - General 5.1.12 Ensure sshd KexAlgorithms is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Key exchange is any method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received Notes: • Kex algorithms have a higher preference the earlier they appear in the list • Some organizations may have stricter requirements for approved Key exchange algorithms • Ensure that Key exchange algorithms used are in compliance with site policy • The only Key Exchange Algorithms currently FIPS 140 approved are: o ecdh-sha2-nistp256 o ecdh-sha2-nistp384 o ecdh-sha2-nistp521 o diffie-hellman-group-exchange-sha256 o diffie-hellman-group16-sha512 o diffie-hellman-group18-sha512 o diffie-hellman-group14-sha256 Rationale: Key exchange methods that are considered weak should be removed. A key exchange method may be weak because too few bits are used, or the hashing algorithm is considered too weak. Using weak algorithms could expose connections to man-in-the- middle attacks Page 509 Internal Only - General Audit: Run the following command to verify none of the "weak" Key Exchange algorithms are being used: # sshd -T | grep -Pi -- 'kexalgorithms\h+([^#\n\r]+,)?(diffie-hellman-group1- sha1|diffie-hellman-group14-sha1|diffie-hellman-group-exchange-sha1)\b' Nothing should be returned. - IF - A line is returned, review the list of Key Exchange Algorithms. The following are considered "weak" Key Exchange Algorithms, and should not be used: diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group-exchange-sha1 Remediation: Edit the /etc/ssh/sshd_config file and add/modify the KexAlgorithms line to contain a comma separated list of the site unapproved (weak) KexAlgorithms preceded with a - above any Include entries: Example: KexAlgorithms -diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie- hellman-group-exchange-sha1 Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: KexAlgorithms sntrup761x25519-sha512@openssh.com,curve25519- sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh- sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16- sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256 References: 1. https://ubuntu.com/server/docs/openssh-crypto-configuration 2. NIST SP 800-53 Rev. 5: SC-8 3. SSHD(8) 4. SSHD_CONFIG(5) Page 510 Internal Only - General Additional Information: The supported algorithms are: curve25519-sha256 curve25519-sha256@libssh.org diffie-hellman-group1-sha1 diffie-hellman-group14-sha1 diffie-hellman-group14-sha256 diffie-hellman-group16-sha512 diffie-hellman-group18-sha512 diffie-hellman-group-exchange-sha1 diffie-hellman-group-exchange-sha256 ecdh-sha2-nistp256 ecdh-sha2-nistp384 ecdh-sha2-nistp521 sntrup4591761x25519-sha512@tinyssh.org CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. Page 511 Internal Only - General 5.1.13 Ensure sshd LoginGraceTime is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The LoginGraceTime parameter specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated connections can exist. Like other session controls in this session the Grace Period should be limited to appropriate organizational limits to ensure the service is available for needed access. Rationale: Setting the LoginGraceTime parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. It will also limit the number of concurrent unauthenticated connections While the recommended setting is 60 seconds (1 Minute), set the number based on site policy. Audit: Run the following command and verify that output LoginGraceTime is between 1 and 60 seconds: # sshd -T | grep logingracetime logingracetime 60 Remediation: Edit the /etc/ssh/sshd_config file to set the LoginGraceTime parameter to 60 seconds or less above any Include entry as follows: LoginGraceTime 60 Note: First occurrence of a option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: LoginGraceTime 120 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-6 3. SSHD(8) Page 512 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 513 Internal Only - General 5.1.14 Ensure sshd LogLevel is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: SSH provides several logging levels with varying amounts of verbosity. The DEBUG options are specifically not recommended other than strictly for debugging SSH communications. These levels provide so much data that it is difficult to identify important security information, and may violate the privacy of users. Rationale: The INFO level is the basic level that only records login activity of SSH users. In many situations, such as Incident Response, it is important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field. The VERBOSE level specifies that login and logout activity as well as the key fingerprint for any SSH key used for login will be logged. This information is important for SSH key management, especially in legacy environments. Audit: Run the following command and verify that output matches loglevel VERBOSE or loglevel INFO: # sshd -T | grep loglevel loglevel VERBOSE - OR - loglevel INFO - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep loglevel Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Page 514 Internal Only - General Remediation: Edit the /etc/ssh/sshd_config file to set the LogLevel parameter to VERBOSE or INFO above any Include and Match entries as follows: LogLevel VERBOSE - OR - LogLevel INFO Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: LogLevel INFO References: 1. https://www.ssh.com/ssh/sshd_config/ 2. NIST SP 800-53 Rev. 5: AU-3, AU-12, SI-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 515 Internal Only - General 5.1.15 Ensure sshd MACs are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: This variable limits the types of MAC algorithms that SSH can use during communication. Notes: • Some organizations may have stricter requirements for approved MACs. • Ensure that MACs used are in compliance with site policy. • The only "strong" MACs currently FIPS 140 approved are: o HMAC-SHA1 o HMAC-SHA2-256 o HMAC-SHA2-384 o HMAC-SHA2-512 Rationale: MD5 and 96-bit MAC algorithms are considered weak and have been shown to increase exploitability in SSH downgrade attacks. Weak algorithms continue to have a great deal of attention as a weak spot that can be exploited with expanded computing power. An attacker that breaks the algorithm could take advantage of a MiTM position to decrypt the SSH tunnel and capture credentials and information. Page 516 Internal Only - General Audit: Run the following command to verify none of the "weak" MACs are being used: # sshd -T | grep -Pi -- 'macs\h+([^#\n\r]+,)?(hmac-md5|hmac-md5-96|hmac- ripemd160|hmac-sha1-96|umac-64@openssh\.com|hmac-md5-etm@openssh\.com|hmac- md5-96-etm@openssh\.com|hmac-ripemd160-etm@openssh\.com|hmac-sha1-96- etm@openssh\.com|umac-64-etm@openssh\.com|umac-128-etm@openssh\.com)\b' Nothing should be returned Note: Review CVE-2023-48795 and verify the system has been patched. If the system has not been patched, review the use of the Encrypt Then Mac (etm) MACs. The following are considered "weak" MACs, and should not be used: hmac-md5 hmac-md5-96 hmac-ripemd160 hmac-sha1-96 umac-64@openssh.com hmac-md5-etm@openssh.com hmac-md5-96-etm@openssh.com hmac-ripemd160-etm@openssh.com hmac-sha1-96-etm@openssh.com umac-64-etm@openssh.com umac-128-etm@openssh.com Remediation: Edit the /etc/ssh/sshd_config file and add/modify the MACs line to contain a comma separated list of the site unapproved (weak) MACs preceded with a - above any Include entries: Example: MACs -hmac-md5,hmac-md5-96,hmac-ripemd160,hmac-sha1-96,umac- 64@openssh.com,hmac-md5-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac- ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,umac-64- etm@openssh.com,umac-128-etm@openssh.com - IF - CVE-2023-48795 has not been reviewed and addressed, the following etm MACs should be added to the exclude list: hmac-sha1-etm@openssh.com,hmac-sha2-256- etm@openssh.com,hmac-sha2-512-etm@openssh.com Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: MACs umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256- etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1- etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2- 256,hmac-sha2-512,hmac-sha1 Page 517 Internal Only - General References: 1. https://nvd.nist.gov/vuln/detail/CVE-2023-48795 2. More information on SSH downgrade attacks can be found here: http://www.mitls.org/pages/attacks/SLOTH 3. SSHD_CONFIG(5) 4. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.10 Encrypt Sensitive Data in Transit v8 Encrypt sensitive data in transit. Example implementations can include: ● ● Transport Layer Security (TLS) and Open Secure Shell (OpenSSH). v7 14.4 Encrypt All Sensitive Information in Transit ● ● Encrypt all sensitive information in transit. 16.5 Encrypt Transmittal of Username and v7 Authentication Credentials ● ● Ensure that all account usernames and authentication credentials are transmitted across networks using encrypted channels. Page 518 Internal Only - General 5.1.16 Ensure sshd MaxAuthTries is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxAuthTries parameter specifies the maximum number of authentication attempts permitted per connection. When the login failure count reaches half the number, error messages will be written to the syslog file detailing the login failure. Rationale: Setting the MaxAuthTries parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. While the recommended setting is 4, set the number based on site policy. Audit: Run the following command and verify that MaxAuthTries is 4 or less: # sshd -T | grep maxauthtries maxauthtries 4 - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep maxauthtries Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit the /etc/ssh/sshd_config file to set the MaxAuthTries parameter to 4 or less above any Include and Match entries as follows: MaxAuthTries 4 Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Page 519 Internal Only - General Default Value: MaxAuthTries 6 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 520 Internal Only - General 5.1.17 Ensure sshd MaxSessions is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxSessions parameter specifies the maximum number of open sessions permitted from a given connection. Rationale: To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions to protect availability of sshd logins and prevent overwhelming the daemon. Audit: Run the following command and verify that MaxSessions is 10 or less: # sshd -T | grep maxsessions maxsessions 10 Run the following command and verify the output: grep -Psi -- '^\h*MaxSessions\h+\"?(1[1-9]|[2-9][0-9]|[1-9][0-9][0-9]+)\b' /etc/ssh/sshd_config /etc/ssh/sshd_config.d/*.conf Nothing should be returned - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep maxsessions Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Page 521 Internal Only - General Remediation: Edit the /etc/ssh/sshd_config file to set the MaxSessions parameter to 10 or less above any Include and Match entries as follows: MaxSessions 10 Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: MaxSessions 10 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 522 Internal Only - General 5.1.18 Ensure sshd MaxStartups is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Rationale: To protect a system from denial of service due to a large number of pending authentication connection attempts, use the rate limiting function of MaxStartups to protect availability of sshd logins and prevent overwhelming the daemon. Audit: Run the following command to verify MaxStartups is 10:30:60 or more restrictive: # sshd -T | awk '$1 ~ /^\s*maxstartups/{split($2, a, ":");{if(a[1] > 10 || a[2] > 30 || a[3] > 60) print $0}}' Nothing should be returned Remediation: Edit the /etc/ssh/sshd_config file to set the MaxStartups parameter to 10:30:60 or more restrictive above any Include entries as follows: MaxStartups 10:30:60 Note: First occurrence of a option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: MaxStartups 10:30:100 References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 523 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 524 Internal Only - General 5.1.19 Ensure sshd PermitEmptyPasswords is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitEmptyPasswords parameter specifies if the SSH server allows login to accounts with empty password strings. Rationale: Disallowing remote shell access to accounts that have an empty password reduces the probability of unauthorized access to the system. Audit: Run the following command to verify PermitEmptyPasswords is set to no: # sshd -T | grep permitemptypasswords permitemptypasswords no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep permitemptypasswords Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit /etc/ssh/sshd_config and set the PermitEmptyPasswords parameter to no above any Include and Match entries as follows: PermitEmptyPasswords no Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Page 525 Internal Only - General Default Value: PermitEmptyPasswords no References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 526 Internal Only - General 5.1.20 Ensure sshd PermitRootLogin is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitRootLogin parameter specifies if the root user can log in using SSH. The default is prohibit-password. Rationale: Disallowing root logins over SSH requires system admins to authenticate using their own individual account, then escalating to root. This limits opportunity for non- repudiation and provides a clear audit trail in the event of a security incident. Audit: Run the following command to verify PermitRootLogin is set to no: # sshd -T | grep permitrootlogin permitrootlogin no - IF - Match set statements are used in your environment, specify the connection parameters to use for the -T extended test mode and run the audit to verify the setting is not incorrectly configured in a match block Example additional audit needed for a match block for the user sshuser: # sshd -T -C user=sshuser | grep permitrootlogin Note: If provided, any Match directives in the configuration file that would apply are applied before the configuration is written to standard output. The connection parameters are supplied as keyword=value pairs and may be supplied in any order, either with multiple -C options or as a comma-separated list. The keywords are addr (source address), user (user), host (resolved source host name), laddr (local address), lport (local port number), and rdomain (routing domain) Remediation: Edit the /etc/ssh/sshd_config file to set the PermitRootLogin parameter to no above any Include and Match entries as follows: PermitRootLogin no Note: First occurrence of an option takes precedence, Match set statements withstanding. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: PermitRootLogin without-password Page 527 Internal Only - General References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5:AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 528 Internal Only - General 5.1.21 Ensure sshd PermitUserEnvironment is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PermitUserEnvironment option allows users to present environment options to the SSH daemon. Rationale: Permitting users the ability to set environment variables through the SSH daemon could potentially allow users to bypass security controls (e.g. setting an execution path that has SSH executing trojan'd programs) Audit: Run the following command to verify PermitUserEnvironment is set to no: # sshd -T | grep permituserenvironment permituserenvironment no Remediation: Edit the /etc/ssh/sshd_config file to set the PermitUserEnvironment parameter to no above any Include entries as follows: PermitUserEnvironment no Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: PermitUserEnvironment no References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1,CM-2, CM-6, CM-7, IA-5 3. SSHD(8) Page 529 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 530 Internal Only - General 5.1.22 Ensure sshd UsePAM is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The UsePAM directive enables the Pluggable Authentication Module (PAM) interface. If set to yes this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication directives in addition to PAM account and session module processing for all authentication types. Rationale: When usePAM is set to yes, PAM runs through account and session types properly. This is important if you want to restrict access to services based off of IP, time or other factors of the account. Additionally, you can make sure users inherit certain environment variables on login or disallow access to the server Audit: Run the following command to verify UsePAM is set to yes: # sshd -T | grep usepam usepam yes Remediation: Edit the /etc/ssh/sshd_config file to set the UsePAM parameter to yes above any Include entries as follows: UsePAM yes Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location. Default Value: UsePAM yes References: 1. SSHD_CONFIG(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 3. SSHD(8) Page 531 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 532 Internal Only - General 5.2 Configure privilege escalation There are various tools which allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. sudo sudo documentation The invoking user's real (not effective) user ID is used to determine the user name with which to query the security policy. sudo supports a plug-in architecture for security policies and input/output logging. Third parties can develop and distribute their own policy and I/O logging plug-ins to work seamlessly with the sudo front end. The default security policy is sudoers, which is configured via the file /etc/sudoers and any entries in /etc/sudoers.d. pkexec pkexec documentation pkexec allows an authorized user to execute PROGRAM as another user. If username is not specified, then the program will be executed as the administrative super user, root. Page 533 Internal Only - General 5.2.1 Ensure sudo is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo allows a permitted user to execute a command as the superuser or another user, as specified by the security policy. The invoking user's real (not effective) user ID is used to determine the user name with which to query the security policy. Rationale: sudo supports a plug-in architecture for security policies and input/output logging. Third parties can develop and distribute their own policy and I/O logging plug-ins to work seamlessly with the sudo front end. The default security policy is sudoers, which is configured via the file /etc/sudoers and any entries in /etc/sudoers.d. The security policy determines what privileges, if any, a user has to run sudo. The policy may require that users authenticate themselves with a password or another authentication mechanism. If authentication is required, sudo will exit if the user's password is not entered within a configurable time limit. This limit is policy-specific. Audit: Run the following command to verify that either sudo is installed: # dpkg-query -s sudo &>/dev/null && echo "sudo is installed" sudo is installed - OR - Run the following command to verify that either sudo-ldap is installed: # dpkg-query -s sudo-ldap &>/dev/null && echo "sudo-ldap is installed" sudo-ldap is installed Remediation: First determine is LDAP functionality is required. If so, then install sudo-ldap, else install sudo. Example: # apt install sudo References: 1. SUDO(8) 2. NIST SP 800-53 Rev. 5: AC-6 Page 534 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 535 Internal Only - General 5.2.2 Ensure sudo commands use pty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo can be configured to run only from a pseudo terminal (pseudo-pty). Rationale: Attackers can run a malicious program using sudo which would fork a background process that remains even when the main program has finished executing. Impact: WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files. Audit: Verify that sudo can only run other commands from a pseudo terminal. Run the following command to verify Defaults use_pty is set: # grep -rPi -- '^\h*Defaults\h+([^#\n\r]+,\h*)?use_pty\b' /etc/sudoers* Verify the output matches: /etc/sudoers:Defaults use_pty Run the follow command to to verify Defaults !use_pty is not set: # grep -rPi -- '^\h*Defaults\h+([^#\n\r]+,\h*)?!use_pty\b' /etc/sudoers* Nothing should be returned Page 536 Internal Only - General Remediation: Edit the file /etc/sudoers with visudo or a file in /etc/sudoers.d/ with visudo -f and add the following line: Defaults use_pty Edit the file /etc/sudoers with visudo and any files in /etc/sudoers.d/ with visudo -f and remove any occurrence of !use_pty Note: • sudo will read each file in /etc/sudoers.d, skipping file names that end in ~ or contain a . character to avoid causing problems with package manager or editor temporary/backup files. • Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second. • Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second. • Using a consistent number of leading zeroes in the file names can be used to avoid such problems. References: 1. SUDO(8) 2. VISUDO(8) 3. sudoers(5) 4. NIST SP 800-53 Rev. 5: AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 537 Internal Only - General 5.2.3 Ensure sudo log file exists (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo can use a custom log file Rationale: A sudo log file simplifies auditing of sudo commands Impact: WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files. Audit: Run the following command to verify that sudo has a custom log file configured: # grep -rPsi "^\h*Defaults\h+([^#]+,\h*)?logfile\h*=\h*(\"|\')?\H+(\"|\')?(,\h*\H+\h*)*\h* (#.*)?$" /etc/sudoers* Verify the output matches: Defaults logfile="/var/log/sudo.log" Remediation: Edit the file /etc/sudoers or a file in /etc/sudoers.d/ with visudo -f and add the following line: Defaults logfile="" Example: Defaults logfile="/var/log/sudo.log" Notes: • sudo will read each file in /etc/sudoers.d, skipping file names that end in ~ or contain a . character to avoid causing problems with package manager or editor temporary/backup files. • Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second. • Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second. • Using a consistent number of leading zeroes in the file names can be used to avoid such problems. Page 538 Internal Only - General References: 1. SUDO(8) 2. VISUDO(8) 3. sudoers(5) 4. NIST SP 800-53 Rev. 5: AU-3, AU-12 Additional Information: visudo edits the sudoers file in a safe fashion, analogous to vipw(8). visudo locks the sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks for parse errors. If the sudoers file is currently being edited you will receive a message to try again later. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 539 Internal Only - General 5.2.4 Ensure users must provide password for escalation (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must be configured so that users must provide a password for privilege escalation. Rationale: Without (re-)authentication, users may access resources or perform tasks for which they do not have authorization. When operating systems provide the capability to escalate a functional capability, it is critical the user (re-)authenticate. Impact: This will prevent automated processes from being able to elevate privileges. Audit: Note: If passwords are not being used for authentication, this is not applicable. Verify the operating system requires users to supply a password for privilege escalation. Check the configuration of the /etc/sudoers and /etc/sudoers.d/* files with the following command: # grep -r "^[^#].*NOPASSWD" /etc/sudoers* If any line is found refer to the remediation procedure below. Remediation: Based on the outcome of the audit procedure, use visudo -f to edit the relevant sudoers file. Remove any line with occurrences of NOPASSWD tags in the file. References: 1. NIST SP 800-53 Rev. 5: AC-6 Page 540 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 541 Internal Only - General 5.2.5 Ensure re-authentication for privilege escalation is not disabled globally (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The operating system must be configured so that users must re-authenticate for privilege escalation. Rationale: Without re-authentication, users may access resources or perform tasks for which they do not have authorization. When operating systems provide the capability to escalate a functional capability, it is critical the user re-authenticate. Audit: Verify the operating system requires users to re-authenticate for privilege escalation. Check the configuration of the /etc/sudoers and /etc/sudoers.d/* files with the following command: # grep -r "^[^#].*\!authenticate" /etc/sudoers* If any line is found with a !authenticate tag, refer to the remediation procedure below. Remediation: Configure the operating system to require users to reauthenticate for privilege escalation. Based on the outcome of the audit procedure, use visudo -f to edit the relevant sudoers file. Remove any occurrences of !authenticate tags in the file(s). References: 1. NIST SP 800-53 Rev. 5: AC-6 Page 542 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 543 Internal Only - General 5.2.6 Ensure sudo timestamp_timeout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: sudo timestamp_timeout controls how long a user's sudo privileges remain active after the initial password entry. Rationale: A timeout value reduces the window of opportunity for unauthorized privileged sudo access. Audit: Ensure that the caching timeout is not disabled and greater than 15 minutes. Run the following command: # grep -roP "timestamp_timeout=\K[0-9]*" /etc/sudoers* If there is no timestamp_timeout configured in /etc/sudoers* then the default of 5 minutes is being used. If the default value is being used, run the following command to verify the default is not disabled or greater than 15 minutes: # sudo -V | grep "Authentication timestamp timeout:" Example output: Authentication timestamp timeout: 15.0 minutes Verify Authentication timestamp timeout: • Is not a negative number (disabled). • Is not greater than 15 minutes, and follows local site policy. • Follows local site policy Page 544 Internal Only - General Remediation: Edit the file listed in the audit section with visudo -f and modify the entry timestamp_timeout= to 15 minutes or less as per your site policy. The value is in minutes. This particular entry may appear on its own, or on the same line as env_reset. See the following two examples: Example 1: Defaults env_reset, timestamp_timeout=15 Example 2: Defaults timestamp_timeout=15 Defaults env_reset Default Value: timestamp_timeout=15 References: 1. https://www.sudo.ws/man/1.9.0/sudoers.man.html 2. NIST SP 800-53 Rev. 5: AC-6 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.4 Restrict Administrator Privileges to Dedicated Administrator Accounts v8 Restrict administrator privileges to dedicated administrator accounts on enterprise assets. Conduct general computing activities, such as internet ● ● ● browsing, email, and productivity suite use, from the user’s primary, non-privileged account. 4.3 Ensure the Use of Dedicated Administrative Accounts v7 Ensure that all users with administrative account access use a dedicated or secondary account for elevated activities. This account should only be used for ● ● ● administrative activities and not internet browsing, email, or similar activities. Page 545 Internal Only - General 5.2.7 Ensure access to the su command is restricted (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The su command allows a user to run a command or shell as another user. The program has been superseded by sudo, which allows for more granular control over privileged access. Normally, the su command can be executed by any user. By uncommenting the pam_wheel.so statement in /etc/pam.d/su, the su command will only allow users in a specific groups to execute su. This group should be empty to reinforce the use of sudo for privileged access. Rationale: Restricting the use of su , and using sudo in its place, provides system administrators better control of the escalation of user privileges to execute privileged commands. The sudo utility also provides a better logging and audit mechanism, as it can log each command executed via sudo , whereas su can only record that a user executed the su program. Audit: Run the following command: # grep -Pi '^\h*auth\h+(?:required|requisite)\h+pam_wheel\.so\h+(?:[^#\n\r]+\h+)?((?!\2) (use_uid\b|group=\H+\b))\h+(?:[^#\n\r]+\h+)?((?!\1)(use_uid\b|group=\H+\b))(\ h+.*)?$' /etc/pam.d/su Verify the output matches: auth required pam_wheel.so use_uid group= Run the following command and verify that the group specified in contains no users: # grep /etc/group Verify the output does not contain any users in the relevant group: :x:: Page 546 Internal Only - General Remediation: Create an empty group that will be specified for use of the su command. The group should be named according to site policy. Example: # groupadd sugroup Add the following line to the /etc/pam.d/su file, specifying the empty group: auth required pam_wheel.so use_uid group=sugroup References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 547 Internal Only - General 5.3 Pluggable Authentication Modules Pluggable Authentication Modules (PAM) is a service that implements modular authentication modules on Linux systems. PAM is implemented as a set of shared objects that are loaded and executed when a program needs to authenticate a user. Files for PAM are typically located in the /etc/pam.d directory. PAM must be carefully configured to secure system authentication. While this section covers some of PAM, please consult other PAM resources to fully understand the configuration capabilities. Note: This section includes guidance that requires the additional modules and the latest version of software packages as covered in the "Configure required security packages" subsection of the "Package Management" section Page 548 Internal Only - General 5.3.1 Configure PAM software packages Updated versions of PAM include additional functionality Page 549 Internal Only - General 5.3.1.1 Ensure latest version of pam is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Linux Pluggable Authentication Modules (PAM) is a suite of libraries that allow a Linux system administrator to configure methods to authenticate users. It provides a flexible and centralized way to switch authentication methods for secured applications by using configuration files instead of changing application code The libpam-runtime provides the runtime support for the PAM library Rationale: Older versions of the libpam-runtime package may not include the latest security and feature patches and updates. Note: This Benchmark was tested against libpam-runtime Version: 1.4.0- 11ubuntu2.6 Audit: Run the following command to verify libpam-runtime is installed: # dpkg-query -s libpam-runtime &>/dev/null && echo "libpam-runtime is installed" libpam-runtime is installed Run the following command to verify libpam-runtime is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-runtime\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-runtime: # apt install libpam-runtime References: 1. PAM(7) Page 550 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 551 Internal Only - General 5.3.1.2 Ensure latest version of libpam-modules is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: libpam-modules is a package containing a set of Pluggable Authentication Modules (PAM) which allows system administrators to configure different authentication methods for user logins, providing flexibility in how users can access applications by using various authentication modules to include password checks and other security mechanisms. Rationale: Older versions of the libpam-modules package may not include the latest security and feature patches and updates. Note: This Benchmark was tested and written against libpam-modules Version: 1.4.0-11ubuntu2.6 Audit: Run the following command to verify libpam-modules is installed: # dpkg-query -s libpam-modules &>/dev/null && echo "libpam-modules is installed" libpam-modules is installed Run the following command to verify libpam-modules is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-modules\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-modules: # apt install libpam-modules CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 552 Internal Only - General 5.3.1.3 Ensure latest version of libpam-pwquality is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: libpwquality provides common functions for password quality checking and scoring them based on their apparent randomness. The library also provides a function for generating random passwords with good pronounceability. This module can be plugged into the password stack of a given service to provide some plug-in strength-checking for passwords. The code was originally based on pam_cracklib module and the module is backwards compatible with its options. Rationale: Strong passwords reduce the risk of systems being hacked through brute force methods. Older versions of the libpam-pwquality package may not include the latest security and feature patches and updates. Note: This Benchmark was tested and written against libpam-pwquality Version: 1.4.4-1build2 Audit: Run the following command to verify libpam-pwquality is installed: # dpkg-query -s libpam-pwquality &>/dev/null && echo "libpam-pwquality is installed" libpam-pwquality is installed Run the following command to verify libpam-pwquality is the latest version: # apt list --upgradable 2>&1 | grep -P '^libpam-pwquality\b' Nothing should be returned Remediation: Run the following command to install the latest version of libpam-pwquality: # apt install libpam-pwquality References: 1. https://packages.debian.org/buster/libpam-pwquality Page 553 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 554 Internal Only - General 5.3.2 Configure pam-auth-update profiles pam-auth-update is a utility that permits configuring the central authentication policy for the system using pre-defined profiles as supplied by PAM module packages. Profiles - Shipped in the /usr/share/pam-configs/ directory specify the modules, with options, to enable; the preferred ordering with respect to other profiles; and whether a profile should be enabled by default. Packages providing PAM modules register their profiles at install time by calling pam-auth-update --package. Selection of profiles is done using the standard debconf interface. The profile selection question will be asked at medium priority when packages are added or removed, so no user interaction is required by default. Users may invoke pam-auth-update directly to change their authentication configuration. The pam-auth-update script makes every effort to respect local changes to /etc/pam.d/common-*. Local modifications to the list of module options will be preserved, and additions of modules within the managed portion of the stack will cause pam-auth-update to treat the config files as locally modified and not make further changes to the config files unless given the --force option. If the user specifies that pam-auth-update should override local configuration changes, the locally-modified files will be saved in /etc/pam.d/ with a suffix of .pam-old. Page 555 Internal Only - General 5.3.2.1 Ensure pam_unix module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: pam_unix is the standard Unix authentication module. It uses standard calls from the system's libraries to retrieve and set account information as well as authentication. Usually this is obtained from the /etc/passwd and if shadow is enabled, the /etc/shadow file as well. The account component performs the task of establishing the status of the user's account and password based on the following shadow elements: expire, last_change, max_change, min_change, warn_change. In the case of the latter, it may offer advice to the user on changing their password or, through the PAM_AUTHTOKEN_REQD return, delay giving service to the user until they have established a new password. The entries listed above are documented in the shadow(5) manual page. Should the user's record not contain one or more of these entries, the corresponding shadow check is not performed. The authentication component performs the task of checking the users credentials (password). The default action of this module is to not permit the user access to a service if their official password is blank. Rationale: The system should only provide access after performing authentication of a user. Audit: Run the following command to verify that pam_unix is enabled: # grep -PH -- '\bpam_unix\.so\b' /etc/pam.d/common- {account,auth,password,session,session-noninteractive} Output should be simular to: /etc/pam.d/common-account:account [success=1 new_authtok_reqd=done default=ignore] pam_unix.so /etc/pam.d/common-auth:auth [success=2 default=ignore] pam_unix.so try_first_pass /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt /etc/pam.d/common-session:session required pam_unix.so /etc/pam.d/common-session-noninteractive:session required pam_unix.so Page 556 Internal Only - General Remediation: Run the following command to enable the pam_unix module: # pam-auth-update --enable unix Note: If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_unix module, enable that module instead References: 1. NIST SP 800-53 Rev. 5: IA-5(1) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 557 Internal Only - General 5.3.2.2 Ensure pam_faillock module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_faillock.so module maintains a list of failed authentication attempts per user during a specified interval and locks the account in case there were more than the configured number of consecutive failed authentications (this is defined by the deny parameter in the faillock configuration). It stores the failure records into per-user files in the tally directory. Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Audit: Run the following commands to verify that pam_faillock is enabled: # grep -P -- '\bpam_faillock\.so\b' /etc/pam.d/common-{auth,account} Output should be similar to: /etc/pam.d/common-auth:auth requisite pam_faillock.so preauth /etc/pam.d/common-auth:auth [default=die] pam_faillock.so authfail /etc/pam.d/common-account:account required pam_faillock.so Page 558 Internal Only - General Remediation: Create two pam-auth-update profiles in /usr/share/pam-configs/: 1. Create the faillock profile in /usr/share/pam-configs/ with the following lines: Name: Enable pam_faillock to deny access Default: yes Priority: 0 Auth-Type: Primary Auth: [default=die] pam_faillock.so authfail Example Script: #!/usr/bin/env bash { arr=('Name: Enable pam_faillock to deny access' 'Default: yes' 'Priority: 0' 'Auth-Type: Primary' 'Auth:' ' [default=die] pam_faillock.so authfail') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/faillock } 2. Create the faillock_notify profile in /usr/share/pam-configs/ with the following lines: Name: Notify of failed login attempts and reset count upon success Default: yes Priority: 1024 Auth-Type: Primary Auth: requisite pam_faillock.so preauth Account-Type: Primary Account: required pam_faillock.so Example Script: #!/usr/bin/env bash { arr=('Name: Notify of failed login attempts and reset count upon success' 'Default: yes' 'Priority: 1024' 'Auth-Type: Primary' 'Auth:' ' requisite pam_faillock.so preauth' 'Account-Type: Primary' 'Account:' ' required pam_faillock.so') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/faillock_notify } Run the following command to update the common-auth and common-account PAM files with the new profiles: # pam-auth-update --enable Example: # pam-auth-update --enable faillock # pam-auth-update --enable faillock_notify Page 559 Internal Only - General Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_faillock module, enable that module instead CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 560 Internal Only - General 5.3.2.3 Ensure pam_pwquality module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwquality.so module performs password quality checking. This module can be plugged into the password stack of a given service to provide strength-checking for passwords. The code was originally based on pam_cracklib module and the module is backwards compatible with its options. The action of this module is to prompt the user for a password and check its strength against a system dictionary and a set of rules for identifying poor choices. The first action is to prompt for a single password, check its strength and then, if it is considered strong, prompt for the password a second time (to verify that it was typed correctly on the first occasion). All being well, the password is passed on to subsequent modules to be installed as the new authentication token. Rationale: Use of a unique, complex passwords helps to increase the time and resources required to compromise the password. Audit: Run the following command to verify that pam_pwquality.so is enabled: # grep -P -- '\bpam_pwquality\.so\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwquality.so retry=3 Page 561 Internal Only - General Remediation: Run the following script to verify the pam_pwquality.so line exists in a pam-auth- update profile: # grep -P -- '\bpam_pwquality\.so\b' /usr/share/pam-configs/* Output should be similar to: /usr/share/pam-configs/pwquality: requisite pam_pwquality.so retry=3 /usr/share/pam-configs/pwquality: requisite pam_pwquality.so retry=3 - IF - similar output is returned: Run the following command to update /etc/pam.d/common-password with the returned profile: # pam-auth-update --enable {PROFILE_NAME} Example: # pam-auth-update pwquality - IF - similar output is NOT returned: Create a pam-auth-update profile in /usr/share/pam-configs/ with the following lines: Name: Pwquality password strength checking Default: yes Priority: 1024 Conflicts: cracklib Password-Type: Primary Password: requisite pam_pwquality.so retry=3 Example: #!/usr/bin/env bash { arr=('Name: Pwquality password strength checking' 'Default: yes' 'Priority: 1024' 'Conflicts: cracklib' 'Password-Type: Primary' 'Password:' ' requisite pam_pwquality.so retry=3') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/pwquality } Run the following command to update /etc/pam.d/common-password with the pwquality profile: # pam-auth-update --enable pwquality Page 562 Internal Only - General Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_pwquality module, enable that module instead CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 563 Internal Only - General 5.3.2.4 Ensure pam_pwhistory module is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwhistory.so module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently. This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking. Rationale: Use of a unique, complex passwords helps to increase the time and resources required to compromise the password. Audit: Run the following command to verify that pam_pwhistory.so is enabled: # grep -P -- '\bpam_pwhistory\.so\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Page 564 Internal Only - General Remediation: Run the following script to verify the pam_pwhistory.so line exists in a pam-auth- update profile: # grep -P -- '\bpam_pwhistory\.so\b' /usr/share/pam-configs/* Output should be similar to: /usr/share/pam-configs/pwhistory: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok - IF - similar output is returned: Run the following command to update /etc/pam.d/common-password with the returned profile: # pam-auth-update --enable {PROFILE_NAME} Example: # pam-auth-update pwhistory - IF - similar output is NOT returned: Create a pwhistory profile in /usr/share/pam-configs/ with the following lines: Name: pwhistory password history checking Default: yes Priority: 1024 Password-Type: Primary Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Example Script: #!/usr/bin/env bash { arr=('Name: pwhistory password history checking' 'Default: yes' 'Priority: 1024' 'Password-Type: Primary' 'Password:' ' requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok') printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/pwhistory } Run the following command to update /etc/pam.d/common-password with the pwhistory profile: # pam-auth-update --enable pwhistory Note: • The name used for the file must be used in the pam-auth-update --enable command • The Name: line should be easily recognizable and understood • The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files • If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_pwhistory module, enable that module instead Page 565 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 566 Internal Only - General 5.3.3 Configure PAM Arguments Pluggable Authentication Modules (PAM) uses arguments to pass information to a pluggable module during authentication for a particular module type. These arguments allow the PAM configuration files for particular programs to use a common PAM module but in different ways. Invalid arguments are ignored and do not otherwise affect the success or failure of the PAM module. When an invalid argument is passed, an error is usually written to /var/log/messages file. However, since the reporting method is controlled by the PAM module, the module must be written correctly to log the error to this file. Note: If custom PAM files are being used, for this section's remediation, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam- auth-update --enable command skipped Page 567 Internal Only - General 5.3.3.1 Configure pam_faillock module pam_faillock.so provides a way to configure the default settings for locking the user after multiple failed authentication attempts. Options: • - The directory where the user files with the failure records are kept. The default is /var/run/faillock. Note: These files will disappear after reboot on systems configured with directory /var/run/faillock mounted on virtual memory. • audit - Will log the user name into the system log if the user is not found. • silent - Don't print informative messages to the user. Please note that when this option is not used there will be difference in the authentication behavior for users which exist on the system and non-existing users. • no_log_info - Don't log informative messages via syslog(3). • local_users_only - Only track failed user authentications attempts for local users in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users. The faillock(8) command will also no longer track user failed authentication attempts. Enabling this option will prevent a double-lockout scenario where a user is locked out locally and in the centralized mechanism. • nodelay - Don't enforce a delay after authentication failures. • deny= - Deny access if the number of consecutive authentication failures for this user during the recent interval exceeds . The default is 3. • fail_interval=n - The length of the interval during which the consecutive authentication failures must happen for the user account lock out is n seconds. The default is 900 (15 minutes). • unlock_time=n - The access will be re-enabled after n seconds after the lock out. The value 0 has the same meaning as value never - the access will not be re-enabled without resetting the faillock entries by the faillock(8) command. The default is 600 (10 minutes). Note that the default directory that pam_faillock uses is usually cleared on system boot so the access will be also re-enabled after system reboot. If that is undesirable a different tally directory must be set with the dir option. Also note that it is usually undesirable to permanently lock out users as they can become easily a target of denial of service attack unless the usernames are random and kept secret to potential attackers. • even_deny_root - Root account can become locked as well as regular accounts. • root_unlock_time=n - This option implies even_deny_root option. Allow access after n seconds to root account after the account is locked. In case the option is not specified the value is the same as of the unlock_time option. • admin_group=name - If a group name is specified with this option, members of the group will be handled by this module the same as the root account (the options even_deny_root and root_unlock_time will apply to them. By default the option is not set. Page 568 Internal Only - General 5.3.3.1.1 Ensure password failed attempts lockout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The deny= option will deny access if the number of consecutive authentication failures for this user during the recent interval exceeds . Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Audit: Run the following command to verify that Number of failed logon attempts before the account is locked is no greater than 5 and meets local site policy: # grep -Pi -- '^\h*deny\h*=\h*[1-5]\b' /etc/security/faillock.conf deny = 5 Run the following command to verify that the deny argument has not been set, or 5 or less and meets local site policy: # grep -Pi -- '^\h*auth\h+(requisite|required|sufficient)\h+pam_faillock\.so\h+([^#\n\r]+\h +)?deny\h*=\h*(0|[6-9]|[1-9][0-9]+)\b' /etc/pam.d/common-auth Nothing should be returned Remediation: Create or edit the following line in /etc/security/faillock.conf setting the deny option to 5 or less: deny = 5 Run the following command: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?deny\b' /usr/share/pam- configs/* Edit any returned files and remove the deny= arguments from the pam_faillock.so line(s): Default Value: deny = 3 Page 569 Internal Only - General Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 570 Internal Only - General 5.3.3.1.2 Ensure password unlock time is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: unlock_time= - The access will be re-enabled after seconds after the lock out. The value 0 has the same meaning as value never - the access will not be re-enabled without resetting the faillock entries by the faillock(8) command. Note: • The default directory that pam_faillock uses is usually cleared on system boot so the access will be also re-enabled after system reboot. If that is undesirable a different tally directory must be set with the dir option. • It is usually undesirable to permanently lock out users as they can become easily a target of denial of service attack unless the usernames are random and kept secret to potential attackers. • The maximum configurable value for unlock_time is 604800 Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Impact: Use of unlock_time=0 may allow an attacker to cause denial of service to legitimate users. This will also require a systems administrator with elevated privileges to unlock the account. Audit: Run the following command to verify that the time in seconds before the account is unlocked is either 0 (never) or 900 (15 minutes) or more and meets local site policy: # grep -Pi -- '^\h*unlock_time\h*=\h*(0|9[0-9][0-9]|[1-9][0-9]{3,})\b' /etc/security/faillock.conf unlock_time = 900 Run the following command to verify that the unlock_time argument has not been set, or is either 0 (never) or 900 (15 minutes) or more and meets local site policy: # grep -Pi -- '^\h*auth\h+(requisite|required|sufficient)\h+pam_faillock\.so\h+([^#\n\r]+\h +)?unlock_time\h*=\h*([1-9]|[1-9][0-9]|[1-8][0-9][0-9])\b' /etc/pam.d/common- auth Nothing should be returned Page 571 Internal Only - General Remediation: Set password unlock time to conform to site policy. unlock_time should be 0 (never), or 900 seconds or greater. Edit /etc/security/faillock.conf and update or add the following line: unlock_time = 900 Run the following command: remove the unlock_time argument from the pam_faillock.so module in the PAM files: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?unlock_time\b' /usr/share/pam-configs/* Edit any returned files and remove the unlock_time= argument from the pam_faillock.so line(s): Default Value: unlock_time = 600 Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 572 Internal Only - General 5.3.3.1.3 Ensure password failed attempts lockout includes root account (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: even_deny_root - Root account can become locked as well as regular accounts root_unlock_time=n - This option implies even_deny_root option. Allow access after n seconds to root account after the account is locked. In case the option is not specified the value is the same as of the unlock_time option. Rationale: Locking out user IDs after n unsuccessful consecutive login attempts mitigates brute force password attacks against your systems. Impact: Use of unlock_time=0 or root_unlock_time=0 may allow an attacker to cause denial of service to legitimate users. Page 573 Internal Only - General Audit: Run the following command to verify that even_deny_root and/or root_unlock_time is enabled: # grep -Pi -- '^\h*(even_deny_root|root_unlock_time\h*=\h*\d+)\b' /etc/security/faillock.conf Example output: even_deny_root --AND/OR-- root_unlock_time = 60 Run the following command to verify that - IF - root_unlock_time is set, it is set to 60 (One minute) or more: # grep -Pi -- '^\h*root_unlock_time\h*=\h*([1-9]|[1-5][0-9])\b' /etc/security/faillock.conf Nothing should be returned Run the following command to check the pam_faillock.so module for the root_unlock_time argument. Verify -IF- root_unlock_time is set, it is set to 60 (One minute) or more: # grep -Pi -- '^\h*auth\h+([^#\n\r]+\h+)pam_faillock\.so\h+([^#\n\r]+\h+)?root_unlock_time\ h*=\h*([1-9]|[1-5][0-9])\b' /etc/pam.d/common-auth Nothing should be returned Remediation: Edit /etc/security/faillock.conf: • Remove or update any line containing root_unlock_time, - OR - set it to a value of 60 or more • Update or add the following line: even_deny_root Run the following command: # grep -Pl -- '\bpam_faillock\.so\h+([^#\n\r]+\h+)?(even_deny_root|root_unlock_time)' /usr/share/pam-configs/* Edit any returned files and remove the even_deny_root and root_unlock_time arguments from the pam_faillock.so line(s): Default Value: disabled Page 574 Internal Only - General Additional Information: If a user has been locked out because they have reached the maximum consecutive failure count defined by deny= in the pam_faillock.so module, the user can be unlocked by issuing the command faillock --user --reset. This command sets the failed count to 0, effectively unlocking the user. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 6.2 Establish an Access Revoking Process Establish and follow a process, preferably automated, for revoking access to v8 enterprise assets, through disabling accounts immediately upon termination, rights ● ● ● revocation, or role change of a user. Disabling accounts, instead of deleting accounts, may be necessary to preserve audit trails. 16.7 Establish Process for Revoking Access Establish and follow an automated process for revoking system access by v7 disabling accounts immediately upon termination or change of responsibilities of an ● ● employee or contractor . Disabling these accounts, instead of deleting accounts, allows preservation of audit trails. Page 575 Internal Only - General 5.3.3.2 Configure pam_pwquality module The pam_pwquality.so module checks the strength of passwords. It performs checks such as making sure a password is not a dictionary word, it is a certain length, contains a mix of characters (e.g. alphabet, numeric, other) and more. These checks are configurable by either: • use of the module arguments • modifying the /etc/security/pwquality.conf configuration file • creating a .conf file in the /etc/security/pwquality.conf.d/ directory. Note: The module arguments override the settings in the /etc/security/pwquality.conf configuration file. Settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory. The possible options in the file are: • difok - Number of characters in the new password that must not be present in the old password. (default 1). The special value of 0 disables all checks of similarity of the new password with the old password except the new password being exactly the same as the old one. • minlen - Minimum acceptable size for the new password (plus one if credits are not disabled which is the default). (See pam_pwquality(8).) Cannot be set to lower value than 6. (default 8) • dcredit - The maximum credit for having digits in the new password. If less than 0 it is the minimum number of digits in the new password. (default 0) • ucredit - The maximum credit for having uppercase characters in the new password. If less than 0 it is the minimum number of uppercase characters in the new password. (default 0) • lcredit - The maximum credit for having lowercase characters in the new password. If less than 0 it is the minimum number of lowercase characters in the new password. (default 0) • ocredit - The maximum credit for having other characters in the new password. If less than 0 it is the minimum number of other characters in the new password. (default 0) • minclass - The minimum number of required classes of characters for the new password (digits, uppercase, lowercase, others). (default 0) • maxrepeat - The maximum number of allowed same consecutive characters in the new password. The check is disabled if the value is 0. (default 0) • maxsequence - The maximum length of monotonic character sequences in the new password. Examples of such sequence are '12345' or 'fedcb'. Note that most such passwords will not pass the simplicity check unless the sequence is only a minor part of the password. The check is disabled if the value is 0. (default 0) Page 576 Internal Only - General • maxclassrepeat - The maximum number of allowed consecutive characters of the same class in the new password. The check is disabled if the value is 0. (default 0) • gecoscheck - If nonzero, check whether the words longer than 3 characters from the GECOS field of the user's passwd(5) entry are contained in the new password. The check is disabled if the value is 0. (default 0) • dictcheck - If nonzero, check whether the password (with possible modifications) matches a word in a dictionary. Currently the dictionary check is performed using the cracklib library. (default 1) • usercheck= - If nonzero, check whether the password (with possible modifications) contains the user name in some form. It is not performed for user names shorter than 3 characters. (default 1) • usersubstr= - If greater than 3 (due to the minimum length in usercheck), check whether the password contains a substring of at least N length in some form. (default 0) • enforcing= - If nonzero, reject the password if it fails the checks, otherwise only print the warning. This setting applies only to the pam_pwquality module and possibly other applications that explicitly change their behavior based on it. It does not affect pwmake(1) and pwscore(1). (default 1) • badwords - Space separated list of words that must not be contained in the password. These are additional words to the cracklib dictionary check. This setting can be also used by applications to emulate the gecos check for user accounts that are not created yet. • dictpath - Path to the cracklib dictionaries. Default is to use the cracklib default. • retry= - Prompt user at most N times before returning with error. The default is 1. • enforce_for_root - The module will return error on failed check even if the user changing the password is root. This option is off by default which means that just the message about the failed check is printed but root can change the password anyway. Note that root is not asked for an old password so the checks that compare the old and new password are not performed. • local_users_only - The module will not test the password quality for users that are not present in the /etc/passwd file. The module still asks for the password so the following modules in the stack can use the use_authtok option. This option is off by default. Page 577 Internal Only - General 5.3.3.2.1 Ensure password number of changed characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality difok option sets the number of characters in a password that must not be present in the old password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the difok option is set to 2 or more and follows local site policy: # grep -Psi -- '^\h*difok\h*=\h*([2-9]|[1-9][0-9]+)\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwdifok.conf:difok = 2 Verify returned value(s) are 2 or more and meet local site policy Run the following command to verify that difok is not set, is 2 or more, and conforms to local site policy: grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?difok\h*=\h*([0-1])\b' /etc/pam.d/common-password Nothing should be returned Page 578 Internal Only - General Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set difok to 2 or more. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*difok\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "difok = 2" > /etc/security/pwquality.conf.d/50-pwdifok.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?difok\b' /usr/share/pam- configs/* Edit any returned files and remove the difok argument from the pam_pwquality.so line(s): Default Value: difok = 1 References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 579 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 580 Internal Only - General 5.3.3.2.2 Ensure minimum password length is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The minimum password length setting determines the lowers number of characters that make up a password for a user account. There are many different theories about how to determine the best password length for an organization, but perhaps "passphrase" is a better term than "password". The minlen option sets the minimum acceptable size for the new password (plus one if credits are not disabled which is the default). Cannot be set to lower value than 6. Rationale: Strong passwords help protect systems from password attacks. Types of password attacks include dictionary attacks, which attempt to use common words and phrases, and brute force attacks, which try every possible combination of characters. Also attackers may try to obtain the account database so they can use tools to discover the accounts and passwords. Impact: In general, it is true that longer passwords are better (harder to crack), but it is also true that forced password length requirements can cause user behavior that is predictable and undesirable. For example, requiring users to have a minimum 16-character password may cause them to choose repeating patterns like fourfourfourfour or passwordpassword that meet the requirement but aren’t hard to guess. Additionally, length requirements increase the chances that users will adopt other insecure practices, like writing them down, re-using them or storing them unencrypted in their documents. Having a reasonable minimum length with no maximum character limit increases the resulting average password length used (and therefore the strength).6 Page 581 Internal Only - General Audit: Run the following command to verify that password length is 14 or more characters, and conforms to local site policy: # grep -Psi -- '^\h*minlen\h*=\h*(1[4-9]|[2-9][0-9]|[1-9][0-9]{2,})\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwlength.conf:minlen = 14 Verify returned value(s) are no less than 14 characters and meet local site policy Run the following command to verify that minlen is not set, or is 14 or more characters, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?minlen\h*=\h*([0-9]|1[0-3])\b' /etc/pam.d/system-auth /etc/pam.d/common-password Nothing should be returned Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 582 Internal Only - General Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set password length of 14 or more characters. Ensure that password length conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*minlen\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "minlen = 14" > /etc/security/pwquality.conf.d/50- pwlength.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?minlen\b' /usr/share/pam- configs/* Edit any returned files and remove the minlen argument from the pam_pwquality.so line(s): Default Value: minlen = 8 References: 1. pam_pwquality(8) 2. CIS Password Policy Guide 3. NIST SP 800-53 Rev. 5: IA-5(1) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 583 Internal Only - General 5.3.3.2.3 Ensure password complexity is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Password complexity can be set through: • minclass - The minimum number of classes of characters required in a new password. (digits, uppercase, lowercase, others). e.g. minclass = 4 requires digits, uppercase, lower case, and special characters. • dcredit - The maximum credit for having digits in the new password. If less than 0 it is the minimum number of digits in the new password. e.g. dcredit = -1 requires at least one digit • ucredit - The maximum credit for having uppercase characters in the new password. If less than 0 it is the minimum number of uppercase characters in the new password. e.g. ucredit = -1 requires at least one uppercase character • ocredit - The maximum credit for having other characters in the new password. If less than 0 it is the minimum number of other characters in the new password. e.g. ocredit = -1 requires at least one special character • lcredit - The maximum credit for having lowercase characters in the new password. If less than 0 it is the minimum number of lowercase characters in the new password. e.g. lcredit = -1 requires at least one lowercase character Rationale: Strong passwords protect systems from being hacked through brute force methods. Requiring at least one non-alphabetic character increases the search space beyond pure dictionary words, which makes the resulting password harder to crack. Forcing users to choose an excessively complex password, e.g. some combination of upper-case, lower-case, numbers, and special characters, has a negative impact. It places an extra burden on users and many will use predictable patterns (for example, a capital letter in the first position, followed by lowercase letters, then one or two numbers, and a “special character” at the end). Attackers know this, so dictionary attacks will often contain these common patterns and use the most common substitutions like, $ for s, @ for a, 1 for l, 0 for o. Impact: Passwords that are too complex in nature make it harder for users to remember, leading to bad practices. In addition, composition requirements provide no defense against common attack types such as social engineering or insecure storage of passwords Page 584 Internal Only - General Audit: Run the following command to verify: • dcredit, ucredit, lcredit, and ocredit are not set to a value greater than 0 • Complexity conforms to local site policy: # grep -Psi -- '^\h*(minclass|[dulo]credit)\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwcomplexity.conf:minclass = 3 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:ucredit = -2 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:lcredit = -2 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:dcredit = -1 /etc/security/pwquality.conf.d/50-pwcomplexity.conf:ocredit = 0 The example represents a requirement of three character classes, with passwords requiring two upper case, two lower case, and one numeric character. Run the following command to verify that module arguments in the configuration file(s) are not being overridden by arguments in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?(minclass=\d*|[dulo]credit=-?\d*)\b' /etc/pam.d/common-password Nothing should be returned Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 585 Internal Only - General Remediation: Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?(minclass|[dulo]credit)\b' /usr/share/pam-configs/* Edit any returned files and remove the minclass, dcredit, ucredit, lcredit, and ocredit arguments from the pam_pwquality.so line(s) Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line(s) to set complexity according to local site policy: • minclass = _N_ • dcredit = _N_ # Value should be either 0 or a number proceeded by a minus (- ) symbol • ucredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol • ocredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol • lcredit = -1 # Value should be either 0 or a number proceeded by a minus (-) symbol Example 1 - Set minclass = 3: #!/usr/bin/env bash { sed -ri 's/^\s*minclass\s*=/# &/' /etc/security/pwquality.conf sed -ri 's/^\s*[dulo]credit\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "minclass = 3" > /etc/security/pwquality.conf.d/50- pwcomplexity.conf } Example 2 - set dcredit = -1, ucredit = -1, and lcredit = -1: #!/usr/bin/env bash { sed -ri 's/^\s*minclass\s*=/# &/' /etc/security/pwquality.conf sed -ri 's/^\s*[dulo]credit\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '%s\n' "dcredit = -1" "ucredit = -1" "lcredit = -1" > /etc/security/pwquality.conf.d/50-pwcomplexity.conf } Page 586 Internal Only - General Default Value: minclass = 0 dcredit = 0 ucredit = 0 ocredit = 0 lcredit = 0 References: 1. pam_pwquality(8) 2. PWQUALITY.CONF(5) 3. https://www.cisecurity.org/insights/white-papers/cis-password-policy-guide 4. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 587 Internal Only - General 5.3.3.2.4 Ensure password same consecutive characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality maxrepeat option sets the maximum number of allowed same consecutive characters in a new password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Audit: Run the following command to verify that the maxrepeat option is set to 3 or less, not 0, and follows local site policy: # grep -Psi -- '^\h*maxrepeat\h*=\h*[1-3]\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwrepeat.conf:maxrepeat = 3 Verify returned value(s) are 3 or less, not 0, and meet local site policy Run the following command to verify that maxrepeat is not set, is 3 or less, not 0, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?maxrepeat\h*=\h*(0|[4-9]|[1-9][0-9]+)\b' /etc/pam.d/common-password Nothing should be returned Page 588 Internal Only - General Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set maxrepeat to 3 or less and not 0. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*maxrepeat\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "maxrepeat = 3" > /etc/security/pwquality.conf.d/50- pwrepeat.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?maxrepeat\b' /usr/share/pam-configs/* Edit any returned files and remove the maxrepeat argument from the pam_pwquality.so line(s): Default Value: maxrepeat = 0 References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 589 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 590 Internal Only - General 5.3.3.2.5 Ensure password maximum sequential characters is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality maxsequence option sets the maximum length of monotonic character sequences in the new password. Examples of such sequence are 12345 or fedcb. The check is disabled if the value is 0. Note: Most such passwords will not pass the simplicity check unless the sequence is only a minor part of the password. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Page 591 Internal Only - General Audit: Run the following command to verify that the maxsequence option is set to 3 or less, not 0, and follows local site policy: # grep -Psi -- '^\h*maxsequence\h*=\h*[1-3]\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwmaxsequence.conf:maxsequence = 3 Verify returned value(s) are 3 or less, not 0, and meet local site policy Run the following command to verify that maxsequence is not set, is 3 or less, not 0, and conforms to local site policy: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?maxsequence\h*=\h*(0|[4-9]|[1-9][0-9]+)\b' /etc/pam.d/common-password Nothing should be returned Note: • settings should be configured in only one location for clarity • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Page 592 Internal Only - General Remediation: Create or modify a file ending in .conf in the /etc/security/pwquality.conf.d/ directory or the file /etc/security/pwquality.conf and add or modify the following line to set maxsequence to 3 or less and not 0. Ensure setting conforms to local site policy: Example: #!/usr/bin/env bash { sed -ri 's/^\s*maxsequence\s*=/# &/' /etc/security/pwquality.conf [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s' "maxsequence = 3" > /etc/security/pwquality.conf.d/50- pwmaxsequence.conf } Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?maxsequence\b' /usr/share/pam-configs/* Edit any returned files and remove the maxsequence argument from the pam_pwquality.so line(s): Default Value: maxsequence = 0 References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 593 Internal Only - General 5.3.3.2.6 Ensure password dictionary check is enabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pwquality dictcheck option sets whether to check for the words from the cracklib dictionary. Rationale: If the operating system allows the user to select passwords based on dictionary words, this increases the chances of password compromise by increasing the opportunity for successful guesses, and brute-force attacks. Page 594 Internal Only - General Audit: Run the following command to verify that the dictcheck option is not set to 0 (disabled) in a pwquality configuration file: # grep -Psi -- '^\h*dictcheck\h*=\h*0\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Nothing should be returned Run the following command to verify that the dictcheck option is not set to 0 (disabled) as a module argument in a PAM file: # grep -Psi -- '^\h*password\h+(requisite|required|sufficient)\h+pam_pwquality\.so\h+([^#\n\ r]+\h+)?dictcheck\h*=\h*0\b' /etc/pam.d/common-password Nothing should be returned Note: • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Edit any file ending in .conf in the /etc/security/pwquality.conf.d/ directory and/or the file /etc/security/pwquality.conf and comment out or remove any instance of dictcheck = 0: Example: # sed -ri 's/^\s*dictcheck\s*=/# &/' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?dictcheck\b' /usr/share/pam-configs/* Edit any returned files and remove the dictcheck argument from the pam_pwquality.so line(s) Default Value: dictcheck = 1 Page 595 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 596 Internal Only - General 5.3.3.2.7 Ensure password quality checking is enforced (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The pam_pwquality module can be configured to either reject a password if it fails the checks, or only print a warning. This is configured by setting the enforcing= argument. If nonzero, a password will be rejected if it fails the checks, otherwise only a warning message will be provided. This setting applies only to the pam_pwquality module and possibly other applications that explicitly change their behavior based on it. It does not affect pwmake(1) and pwscore(1). Rationale: Strong passwords help protect systems from password attacks. Types of password attacks include dictionary attacks, which attempt to use common words and phrases, and brute force attacks, which try every possible combination of characters. Also attackers may try to obtain the account database so they can use tools to discover the accounts and passwords. Audit: Run the following command to verify that enforcing=0 has not been set in a pwquality configuration file: # grep -PHsi -- '^\h*enforcing\h*=\h*0\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Nothing should be returned Run the following command to verify that the enforcing=0 argument has not been set on the pam_pwquality module: # grep -PHsi -- '^\h*password\h+[^#\n\r]+\h+pam_pwquality\.so\h+([^#\n\r]+\h+)?enforcing=0\b' /etc/pam.d/common-password Nothing should be returned Page 597 Internal Only - General Remediation: Run the following command: # grep -Pl -- '\bpam_pwquality\.so\h+([^#\n\r]+\h+)?enforcing=0\b' /usr/share/pam-configs/* Edit any returned files and remove the enforcing=0 argument from the pam_pwquality.so line(s) Edit /etc/security/pwquality.conf and all files ending in .conf in the /etc/security/pwquality.conf.d/ directory and remove or comment out any line containing the enforcing = 0 argument: Example: # sed -ri 's/^\s*enforcing\s*=\s*0/# &/' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Default Value: enforcing=1 References: 1. pam_pwquality(8) 2. PWQUALITY.CONF(5) 3. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 598 Internal Only - General 5.3.3.2.8 Ensure password quality is enforced for the root user (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: If the pwquality enforce_for_root option is enabled, the module will return error on failed check even if the user changing the password is root. This option is off by default which means that just the message about the failed check is printed but root can change the password anyway. Note: The root is not asked for an old password so the checks that compare the old and new password are not performed. Rationale: Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Page 599 Internal Only - General Audit: Run the following command to verify that the enforce_for_root option is enabled in a pwquality configuration file: # grep -Psi -- '^\h*enforce_for_root\b' /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf Example output: /etc/security/pwquality.conf.d/50-pwroot.conf:enforce_for_root Note: • Settings observe an order of precedence: o module arguments override the settings in the /etc/security/pwquality.conf configuration file o settings in the /etc/security/pwquality.conf configuration file override settings in a .conf file in the /etc/security/pwquality.conf.d/ directory o settings in a .conf file in the /etc/security/pwquality.conf.d/ directory are read in canonical order, with last read file containing the setting taking precedence • It is recommended that settings be configured in a .conf file in the /etc/security/pwquality.conf.d/ directory for clarity, convenience, and durability. Remediation: Edit or add the following line in a *.conf file in /etc/security/pwquality.conf.d or in /etc/security/pwquality.conf: Example: #!/usr/bin/env bash { [ ! -d /etc/security/pwquality.conf.d/ ] && mkdir /etc/security/pwquality.conf.d/ printf '\n%s\n' "enforce_for_root" > /etc/security/pwquality.conf.d/50- pwroot.conf } Default Value: disabled References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 600 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 601 Internal Only - General 5.3.3.3 Configure pam_pwhistory module pam_pwhistory - PAM module to remember last passwords pam_history.so module - This module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently. This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking. Options: • debug - Turns on debugging via syslog(3). • use_authtok - When password changing enforce the module to use the new password provided by a previously stacked password module (this is used in the example of the stacking of the pam_passwdqc module documented below). • enforce_for_root - If this option is set, the check is enforced for root, too. • remember= - The last passwords for each user are saved. The default is 10. Value of 0 makes the module to keep the existing contents of the opasswd file unchanged. • retry= - Prompt user at most times before returning with error. The default is 1. • authtok_type= - See pam_get_authtok(3) for more details. Examples: An example password section would be: #%PAM-1.0 password required pam_pwhistory.so password required pam_unix.so use_authtok In combination with pam_passwdqc: #%PAM-1.0 password required pam_passwdqc.so config=/etc/passwdqc.conf password required pam_pwhistory.so use_authtok password required pam_unix.so use_authtok Page 602 Internal Only - General 5.3.3.3.1 Ensure password history remember is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/security/opasswd file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords. The number of passwords remembered is set via the remember argument value in set for the pam_pwhistory module. • remember= - is the number of old passwords to remember Rationale: Requiring users not to reuse their passwords make it less likely that an attacker will be able to guess the password or use a compromised password. Note: These change only apply to accounts configured on the local system. Audit: Run the following command and verify: • The pwhistory line in /etc/pam.d/common-password includes remember= • The value of is 24 or more • The value meets local site policy # grep -Psi -- '^\h*password\h+[^#\n\r]+\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?remember=\d+\b ' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Page 603 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_pwhistory\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files and edit or add the remember= argument, with a value of 24 or more, that meets local site policy to the pam_pwhistory line in the Password section: Example File: Name: pwhistory password history checking Default: yes Priority: 1024 Password-Type: Primary Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok # <- **ensure line includes remember=** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable pwhistory References: 1. NIST SP 800-53 Rev. 5: IA-5(1) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 604 Internal Only - General 5.3.3.3.2 Ensure password history is enforced for the root user (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: If the pwhistory enforce_for_root option is enabled, the module will enforce password history for the root user as well Rationale: Requiring users not to reuse their passwords make it less likely that an attacker will be able to guess the password or use a compromised password Note: These change only apply to accounts configured on the local system. Audit: Run the following command to verify that the enforce_for_root argument is exists on the pwhistory line in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+[^#\n\r]+\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?enforce_for_ro ot\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Page 605 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_pwhistory\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files and add the enforce_for_root argument to the pam_pwhistory line in the Password section: Example File: Name: pwhistory password history checking Default: yes Priority: 1024 Password-Type: Primary Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok # <- **ensure line includes enforce_for_root** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable pwhistory Default Value: disabled References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 606 Internal Only - General 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: use_authtok - When password changing enforce the module to set the new password to the one provided by a previously stacked password module Rationale: use_authtok allows multiple pam modules to confirm a new password before it is accepted. Audit: Run the following command to verify that the use_authtok argument exists on the pwhistory line in /etc/pam.d/common-password: # grep -Psi -- '^\h*password\h+[^#\n\r]+\h+pam_pwhistory\.so\h+([^#\n\r]+\h+)?use_authtok\b' /etc/pam.d/common-password Output should be similar to: password requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok Page 607 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_pwhistory\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files and add the use_authtok argument to the pam_pwhistory line in the Password section: Example File: Name: pwhistory password history checking Default: yes Priority: 1024 Password-Type: Primary Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok # <- **ensure line includes use_authtok** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable pwhistory References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 608 Internal Only - General 5.3.3.4 Configure pam_unix module The pam_unix.so module is the standard Unix authentication module. It uses standard calls from the system's libraries to retrieve and set account information as well as authentication. Usually this is obtained from the /etc/passwd and the /etc/shadow file as well if shadow is enabled. Page 609 Internal Only - General 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The nullok argument overrides the default action of pam_unix.so to not permit the user access to a service if their official password is blank. Rationale: Using a strong password is essential to helping protect personal and sensitive information from unauthorized access Audit: Run the following command to verify that the nullok argument is not set on the pam_unix.so module: # grep -PHs -- '^\h*[^#\n\r]+\h+pam_unix\.so\h+([^#\n\r]+\h+)?nullok\b' /etc/pam.d/common-{password,auth,account,session,session-noninteractive} Nothing should be returned Page 610 Internal Only - General Remediation: Run the following command: # grep -PH -- '^\h*([^#\n\r]+\h+)?pam_unix\.so\h+([^#\n\r]+\h+)?nullok\b' /usr/share/pam-configs/* Edit any files returned and remove the nullok argument for the pam_unix lines Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary Auth: [success=end default=ignore] pam_unix.so try_first_pass # <- **ensure line does not include nullok nullok** Auth-Initial: [success=end default=ignore] pam_unix.so # <- **ensure line does not include nullok nullok** Account-Type: Primary Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix Note: If custom files are being used, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam-auth-update --enable command skipped Page 611 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 612 Internal Only - General 5.3.3.4.2 Ensure pam_unix does not include remember (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The remember=n argument saves the last n passwords for each user in /etc/security/opasswd in order to force password change history and keep the user from alternating between the same password too frequently. The MD5 password hash algorithm is used for storing the old passwords. Instead of this option the pam_pwhistory module should be used. The pam_pwhistory module saves the last n passwords for each user in /etc/security/opasswd using the password hash algorithm set on the pam_unix module. This allows for the yescrypt or sha512 hash algorithm to be used. Rationale: The remember=n argument should be removed to ensure a strong password hashing algorithm is being used. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local user's old passwords stored in /etc/security/opasswd. Audit: Run the following command to verify that the remember argument is not set on the pam_unix.so module: # grep -PHs -- '^\h*^\h*[^#\n\r]+\h+pam_unix\.so\h+([^#\n\r]+\h+)?remember=\d+\b' /etc/pam.d/common-{password,auth,account,session,session-noninteractive} Nothing should be returned Page 613 Internal Only - General Remediation: Run the following command: # grep -PH -- '^\h*([^#\n\r]+\h+)?pam_unix\.so\h+([^#\n\r]+\h+)?remember\b' /usr/share/pam-configs/* Edit any files returned and remove the remember=__ argument for the pam_unix lines Example output: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt remember=5 # **<- remove remember=** [success=end default=ignore] pam_unix.so obscure yescrypt remember=5 # **<- remove remember=** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix Note: If custom files are being used, the corresponding files in /etc/pam.d/ would need to be edited directly, and the pam-auth-update --enable command skipped CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 614 Internal Only - General 5.3.3.4.3 Ensure pam_unix includes a strong password hashing algorithm (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A cryptographic hash function converts an arbitrary-length input into a fixed length output. Password hashing performs a one-way transformation of a password, turning the password into another string, called the hashed password. The pam_unix module can be configured to use one of the following hashing algorithms for user's passwords: • md5 - When a user changes their password next, encrypt it with the MD5 algorithm. • bigcrypt - When a user changes their password next, encrypt it with the DEC C2 algorithm. • sha256 - When a user changes their password next, encrypt it with the SHA256 algorithm. The SHA256 algorithm must be supported by the crypt(3) function. • sha512 - When a user changes their password next, encrypt it with the SHA512 algorithm. The SHA512 algorithm must be supported by the crypt(3) function. • blowfish - When a user changes their password next, encrypt it with the blowfish algorithm. The blowfish algorithm must be supported by the crypt(3) function. • gost_yescrypt - When a user changes their password next, encrypt it with the gost-yescrypt algorithm. The gost-yescrypt algorithm must be supported by the crypt(3) function. • yescrypt - When a user changes their password next, encrypt it with the yescrypt algorithm. The yescrypt algorithm must be supported by the crypt(3) function. Rationale: The SHA-512 and yescrypt algorithms provide a stronger hash than other algorithms used by Linux for password hash generation. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local user passwords. Note: These changes only apply to the local system. Page 615 Internal Only - General Audit: Run the following command to verify that a strong password hashing algorithm is set on the pam_unix.so module: # grep -PH -- '^\h*password\h+([^#\n\r]+)\h+pam_unix\.so\h+([^#\n\r]+\h+)?(sha512|yescrypt) \b' /etc/pam.d/common-password Output should be similar to: /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Verify that the line(s) include either sha512 - OR - yescrypt Page 616 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_unix\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files and edit or add a strong hashing algorithm, either sha512 or yescrypt, that meets local site policy to the pam_unix lines in the Password section: Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary # <- Start of "Auth" section Auth: [success=end default=ignore] pam_unix.so try_first_pass Auth-Initial: [success=end default=ignore] pam_unix.so Account-Type: Primary # <- Start of "Account" section Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional # <- Start of "Session" section Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary # <- Start of "Password" section Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt # <- **ensure hashing algorithm is either sha512 or yescrypt** Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt # <- **ensure hashing algorithm is either sha512 or yescrypt** Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 617 Internal Only - General Additional Information: The following command may be used to expire all non-system user ID's immediately and force them to change their passwords on next login. Any system accounts that need to be expired should be carefully done separately by the system administrator to prevent any potential problems. # awk -F: '( $3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' && $1 != "nfsnobody" ) { print $1 }' /etc/passwd | xargs -n 1 chage -d 0 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 618 Internal Only - General 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: use_authtok - When password changing enforce the module to set the new password to the one provided by a previously stacked password module Rationale: use_authtok allows multiple pam modules to confirm a new password before it is accepted. Audit: Run the following command to verify that use_authtok is set on the pam_unix.so module lines in the password stack: # grep -PH -- '^\h*password\h+([^#\n\r]+)\h+pam_unix\.so\h+([^#\n\r]+\h+)?use_authtok\b' /etc/pam.d/common-password Output should be similar to: /etc/pam.d/common-password:password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt Verify that the line(s) include use_authtok Page 619 Internal Only - General Remediation: Run the following command: # awk '/Password-Type:/{ f = 1;next } /-Type:/{ f = 0 } f {if (/pam_unix\.so/) print FILENAME}' /usr/share/pam-configs/* Edit any returned files add use_authtok to the pam_unix line in the Password section under Password: subsection: Note: The if the file's Password section includes a Password-Initial: subsection, use_authtok should not be added to the pam_unix line in the Password-Initial: subsection Example File: Name: Unix authentication Default: yes Priority: 256 Auth-Type: Primary # <- Start of "Auth" section Auth: [success=end default=ignore] pam_unix.so try_first_pass Auth-Initial: [success=end default=ignore] pam_unix.so Account-Type: Primary # <- Start of "Account" section Account: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Account-Initial: [success=end new_authtok_reqd=done default=ignore] pam_unix.so Session-Type: Additional # <- Start of "Session" section Session: required pam_unix.so Session-Initial: required pam_unix.so Password-Type: Primary # <- Start of "Password" section Password: [success=end default=ignore] pam_unix.so obscure use_authtok try_first_pass yescrypt # <- **ensure line includes use_authtok** Password-Initial: [success=end default=ignore] pam_unix.so obscure yescrypt # <- **Password-Initial: subsection does not include use_authtok Run the following command to update the files in the /etc/pam.d/ directory: # pam-auth-update --enable Example: # pam-auth-update --enable unix References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 620 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. 5.4 User Accounts and Environment This section provides guidance on setting up secure defaults for system and user accounts and their environment. Page 621 Internal Only - General 5.4.1 Configure shadow password suite parameters While a majority of the password control parameters have been moved to PAM, some parameters are still available through the shadow password suite. Any changes made to /etc/login.defs will only be applied if the usermod command is used. If user IDs are added a different way, use the chage command to effect changes to individual user IDs. Page 622 Internal Only - General 5.4.1.1 Ensure password expiration is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PASS_MAX_DAYS parameter in /etc/login.defs allows an administrator to force passwords to expire once they reach a defined age. PASS_MAX_DAYS - The maximum number of days a password may be used. If the password is older than this, a password change will be forced. If not specified, -1 will be assumed (which disables the restriction). Rationale: The window of opportunity for an attacker to leverage compromised credentials or successfully compromise credentials via an online brute force attack is limited by the age of the password. Therefore, reducing the maximum age of a password also reduces an attacker's window of opportunity. We recommend a yearly password change. This is primarily because for all their good intentions users will share credentials across accounts. Therefore, even if a breach is publicly identified, the user may not see this notification, or forget they have an account on that site. This could leave a shared credential vulnerable indefinitely. Having an organizational policy of a 1-year (annual) password expiration is a reasonable compromise to mitigate this with minimal user burden. Impact: The password expiration must be greater than the minimum days between password changes or users will be unable to change their password. Excessive password expiration requirements do more harm than good, because these requirements make users select predictable passwords, composed of sequential words and numbers that are closely related to each other. In these cases, the next password can be predicted based on the previous one (incrementing a number used in the password for example). Also, password expiration requirements offer no containment benefits because attackers will often use credentials as soon as they compromise them. Instead, immediate password changes should be based on key events including, but not limited to: • Indication of compromise • Change of user roles • When a user leaves the organization. Page 623 Internal Only - General Not only does changing passwords every few weeks or months frustrate the user, but it’s also been suggested that it does more harm than good, because it could lead to bad practices by the user such as adding a character to the end of their existing password. Audit: Run the following command and verify PASS_MAX_DAYS is set to 365 days or less and conforms to local site policy: # grep -Pi -- '^\h*PASS_MAX_DAYS\h+\d+\b' /etc/login.defs Example output: PASS_MAX_DAYS 365 Run the following command to verify all /etc/shadow passwords PASS_MAX_DAYS: • is greater than 0 days • is less than or equal to 365 days • conforms to local site policy # awk -F: '($2~/^\$.+\$/) {if($5 > 365 || $5 < 1)print "User: " $1 " PASS_MAX_DAYS: " $5}' /etc/shadow Nothing should be returned Remediation: Set the PASS_MAX_DAYS parameter to conform to site policy in /etc/login.defs : PASS_MAX_DAYS 365 Modify user parameters for all users with a password set to match: # chage --maxdays 365 Edit /etc/login.defs and set PASS_MAX_DAYS to a value greater than 0 that follows local site policy: Example: PASS_MAX_DAYS 365 Run the following command to modify user parameters for all users with a password set to a maximum age no greater than 365 or less than 1 that follows local site policy: # chage --maxdays Example: # awk -F: '($2~/^\$.+\$/) {if($5 > 365 || $5 < 1)system ("chage --maxdays 365 " $1)}' /etc/shadow Warning: If a password has been set at system install or kickstart, the last change date field is not set, In this case, setting PASS_MAX_DAYS will immediately expire the password. One possible solution is to populate the last change date field through a command like: chage -d "$(date +%Y-%m-%d)" root Default Value: PASS_MAX_DAYS 99999 Page 624 Internal Only - General References: 1. CIS Password Policy Guide 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Additional Information: A value of -1 will disable password expiration. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 625 Internal Only - General 5.4.1.2 Ensure minimum password days is configured (Manual) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: PASS_MIN_DAYS - The minimum number of days allowed between password changes. Any password changes attempted sooner than this will be rejected. If not specified, 0 will be assumed (which disables the restriction). Rationale: Users may have favorite passwords that they like to use because they are easy to remember and they believe that their password choice is secure from compromise. Unfortunately, passwords are compromised and if an attacker is targeting a specific individual user account, with foreknowledge of data about that user, reuse of old, potentially compromised passwords, may cause a security breach. By restricting the frequency of password changes, an administrator can prevent users from repeatedly changing their password in an attempt to circumvent password reuse controls Impact: If a users password is set by other personnel as a procedure in dealing with a lost or expired password, the user should be forced to update this "set" password with their own password. e.g. force "change at next logon". If it is not possible to have a user set their own password immediately, and this recommendation or local site procedure may cause a user to continue using a third party generated password, PASS_MIN_DAYS for the effected user should be temporally changed to 0via chage --mindays , to allow a user to change their password immediately. For applications where the user is not using the password at console, the ability to "change at next logon" may be limited. This may cause a user to continue to use a password created by other personnel. Page 626 Internal Only - General Audit: Run the following command to verify that PASS_MIN_DAYS is set to a value greater than 0 and follows local site policy: # grep -Pi -- '^\h*PASS_MIN_DAYS\h+\d+\b' /etc/login.defs Example output: PASS_MIN_DAYS 1 Run the following command to verify all passwords have a PASS_MIN_DAYS greater than 0: # awk -F: '($2~/^\$.+\$/) {if($4 < 1)print "User: " $1 " PASS_MIN_DAYS: " $4}' /etc/shadow Nothing should be returned Remediation: Edit /etc/login.defs and set PASS_MIN_DAYS to a value greater than 0 that follows local site policy: Example: PASS_MIN_DAYS 1 Run the following command to modify user parameters for all users with a password set to a minimum days greater than zero that follows local site policy: # chage --mindays Example: # awk -F: '($2~/^\$.+\$/) {if($4 < 1)system ("chage --mindays 1 " $1)}' /etc/shadow Default Value: PASS_MIN_DAYS 0 References: 1. CIS Password Policy Guide 2. NIST SP 800-53 :: IA-5 (1) (d) 3. NIST SP 800-53A :: IA-5 (1).1 (v) 4. STIG ID: RHEL-08-020180 | Rule ID: SV-230364r627750 | CAT II 5. STIG ID: RHEL-08-020190 | Rule ID: SV-230365r858727 | CAT II 6. STIG ID: UBTU-20-010007 | Rule ID: SV-238202r1015140 | CAT III 7. STIG ID: UBTU-22-411025 | Rule ID: SV-260545r1015007 | CAT III Page 627 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 628 Internal Only - General 5.4.1.3 Ensure password expiration warning days is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The PASS_WARN_AGE parameter in /etc/login.defs allows an administrator to notify users that their password will expire in a defined number of days. PASS_WARN_AGE - The number of days warning given before a password expires. A zero means warning is given only upon the day of expiration, a negative value means no warning is given. If not specified, no warning will be provided. Rationale: Providing an advance warning that a password will be expiring gives users time to think of a secure password. Users caught unaware may choose a simple password or write it down where it may be discovered. Audit: Run the following command and verify PASS_WARN_AGE is 7 or more and follows local site policy: # grep -Pi -- '^\h*PASS_WARN_AGE\h+\d+\b' /etc/login.defs Example output: PASS_WARN_AGE 7 Run the following command to verify all passwords have a PASS_WARN_AGE of 7 or more: # awk -F: '($2~/^\$.+\$/) {if($6 < 7)print "User: " $1 " PASS_WARN_AGE: " $6}' /etc/shadow Nothing should be returned Page 629 Internal Only - General Remediation: Edit /etc/login.defs and set PASS_WARN_AGE to a value of 7 or more that follows local site policy: Example: PASS_WARN_AGE 7 Run the following command to modify user parameters for all users with a password set to a minimum warning to 7 or more days that follows local site policy: # chage --warndays Example: # awk -F: '($2~/^\$.+\$/) {if($6 < 7)system ("chage --warndays 7 " $1)}' /etc/shadow Default Value: PASS_WARN_AGE 7 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 630 Internal Only - General 5.4.1.4 Ensure strong password hashing algorithm is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: A cryptographic hash function converts an arbitrary-length input into a fixed length output. Password hashing performs a one-way transformation of a password, turning the password into another string, called the hashed password. ENCRYPT_METHOD (string) - This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line). It can take one of these values: • MD5 - MD5-based algorithm will be used for encrypting password • SHA256 - SHA256-based algorithm will be used for encrypting password • SHA512 - SHA512-based algorithm will be used for encrypting password • BCRYPT - BCRYPT-based algorithm will be used for encrypting password • YESCRYPT - YESCRYPT-based algorithm will be used for encrypting password • DES - DES-based algorithm will be used for encrypting password (default) Note: • This parameter overrides the deprecated MD5_CRYPT_ENAB variable. • This parameter will only affect the generation of group passwords. • The generation of user passwords is done by PAM and subject to the PAM configuration. • It is recommended to set this variable consistently with the PAM configuration. Rationale: The SHA-512 and yescrypt algorithms provide a stronger hash than other algorithms used by Linux for password hash generation. A stronger hash provides additional protection to the system by increasing the level of effort needed for an attacker to successfully determine local group passwords. Page 631 Internal Only - General Audit: Run the following command to verify the hashing algorithm is sha512 or yescrypt in /etc/login.defs: # grep -Pi -- '^\h*ENCRYPT_METHOD\h+(SHA512|YESCRYPT)\b' /etc/login.defs Example output: ENCRYPT_METHOD SHA512 - OR - ENCRYPT_METHOD YESCRYPT Remediation: Edit /etc/login.defs and set the ENCRYPT_METHOD to SHA512 or YESCRYPT: ENCRYPT_METHOD Example: ENCRYPT_METHOD YESCRYPT Note: • This only effects local groups' passwords created after updating the file to use sha512 or yescrypt. • If it is determined that the password algorithm being used is not sha512 or yescrypt, once it is changed, it is recommended that all group passwords be updated to use the stronger hashing algorithm. • It is recommended that the chosen hashing algorithm is consistent across /etc/login.defs and the PAM configuration Default Value: ENCRYPT_METHOD SHA512 References: 1. NIST SP 800-53 Rev. 5: IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 632 Internal Only - General 5.4.1.5 Ensure inactive password lock is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: User accounts that have been inactive for over a given period of time can be automatically disabled. INACTIVE - Defines the number of days after the password exceeded its maximum age where the user is expected to replace this password. The value is stored in the shadow password file. An input of 0 will disable an expired password with no delay. An input of -1 will blank the respective field in the shadow password file. Rationale: Inactive accounts pose a threat to system security since the users are not logging in to notice failed login attempts or other anomalies. Audit: Run the following command and verify INACTIVE conforms to site policy (no more than 45 days): # useradd -D | grep INACTIVE INACTIVE=45 Verify all users with a password have Password inactive no more than 45 days after password expires Verify all users with a password have Password inactive no more than 45 days after password expires: Run the following command and Review list of users and INACTIVE to verify that all users INACTIVE conforms to site policy (no more than 45 days): # awk -F: '($2~/^\$.+\$/) {if($7 > 45 || $7 < 0)print "User: " $1 " INACTIVE: " $7 "Days"}' /etc/shadow Nothing should be returned Page 633 Internal Only - General Remediation: Run the following command to set the default password inactivity period to 45 days or less that meets local site policy: # useradd -D -f Example: # useradd -D -f 45 Run the following command to modify user parameters for all users with a password set to a inactive age of 45 days or less that follows local site policy: # chage --inactive Example: # awk -F: '($2~/^\$.+\$/) {if($7 > 45 || $7 < 0)system ("chage --inactive 45 " $1)}' /etc/shadow Default Value: INACTIVE=-1 References: 1. CIS Password Policy Guide Additional Information: A value of -1 would disable this setting. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 634 Internal Only - General 5.4.1.6 Ensure all users last password change date is in the past (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: All users should have a password change date in the past. Rationale: If a user's recorded password change date is in the future, then they could bypass any set password expiration. Audit: Run the following script and verify nothing is returned: #!/usr/bin/env bash { while IFS= read -r l_user; do l_change=$(date -d "$(chage --list $l_user | grep '^Last password change' | cut -d: -f2 | grep -v 'never$')" +%s) if [[ "$l_change" -gt "$(date +%s)" ]]; then echo "User: \"$l_user\" last password change was \"$(chage --list $l_user | grep '^Last password change' | cut -d: -f2)\"" fi done < <(awk -F: '$2~/^\$.+\$/{print $1}' /etc/shadow) } Remediation: Investigate any users with a password change date in the future and correct them. Locking the account, expiring the password, or resetting the password manually may be appropriate. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 635 Internal Only - General 5.4.2 Configure root and system accounts and environment Page 636 Internal Only - General 5.4.2.1 Ensure root is the only UID 0 account (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Any account with UID 0 has superuser privileges on the system. Rationale: This access must be limited to only the default root account and only from the system console. Administrative access must be through an unprivileged account using an approved mechanism as noted in the Recommendation "Ensure access to the su command is restricted". Audit: Run the following command and verify that only "root" is returned: # awk -F: '($3 == 0) { print $1 }' /etc/passwd root Remediation: Run the following command to change the root account UID to 0: # usermod -u 0 root Modify any users other than root with UID 0 and assign them a new UID. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 637 Internal Only - General 5.4.2.2 Ensure root is the only GID 0 account (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The usermod command can be used to specify which group the root account belongs to. This affects permissions of files that are created by the root account. Rationale: Using GID 0 for the root account helps prevent root -owned files from accidentally becoming accessible to non-privileged users. Audit: Run the following command to verify the root user's primary GID is 0, and no other user's have GID 0 as their primary GID: # awk -F: '($1 !~ /^(sync|shutdown|halt|operator)/ && $4=="0") {print $1":"$4}' /etc/passwd root:0 Note: User's: sync, shutdown, halt, and operator are excluded from the check for other user's with GID 0 Remediation: Run the following command to set the root user's GID to 0: # usermod -g 0 root Run the following command to set the root group's GID to 0: # groupmod -g 0 root Remove any users other than the root user with GID 0 or assign them a new GID if appropriate. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 638 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 639 Internal Only - General 5.4.2.3 Ensure group root is the only GID 0 group (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The groupmod command can be used to specify which group the root group belongs to. This affects permissions of files that are group owned by the root group. Rationale: Using GID 0 for the root group helps prevent root group owned files from accidentally becoming accessible to non-privileged users. Audit: Run the following command to verify no group other than root is assigned GID 0: # awk -F: '$3=="0"{print $1":"$3}' /etc/group root:0 Remediation: Run the following command to set the root group's GID to 0: # groupmod -g 0 root Remove any groups other than the root group with GID 0 or assign them a new GID if appropriate. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 640 Internal Only - General 5.4.2.4 Ensure root account access is controlled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of methods to access the root account directly. Without a password set any user would be able to gain access and thus control over the entire system. Rationale: Access to root should be secured at all times. Impact: If there are any automated processes that relies on access to the root account without authentication, they will fail after remediation. Audit: Run the following command to verify that either the root user's password is set or the root user's account is locked: # passwd -S root | awk '$2 ~ /^(P|L)/ {print "User: \"" $1 "\" Password is status: " $2}' Verify the output is either: User: "root" Password is status: P - OR - User: "root" Password is status: L Note: • P - Password is set • L - Password is locked Remediation: Run the following command to set a password for the root user: # passwd root - OR - Run the following command to lock the root user account: # usermod -L root Page 641 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 642 Internal Only - General 5.4.2.5 Ensure root path integrity (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The root user can execute any command on the system and could be fooled into executing programs unintentionally if the PATH is not set correctly. Rationale: Including the current working directory (.) or other writable directory in root's executable path makes it likely that an attacker can gain superuser access by forcing an administrator operating as root to execute a Trojan horse program. Page 643 Internal Only - General Audit: Run the following script to verify root's path does not include: • Locations that are not directories • An empty directory (::) • A trailing (:) • Current working directory (.) • Non root owned directories • Directories that less restrictive than mode 0755 #!/usr/bin/env bash { a_output2=() l_pmask="0022" l_maxperm="$( printf '%o' $(( 0777 & ~$l_pmask )) )" l_root_path="$(sudo su - root -c env | awk -F= '$1=="PATH"{print $2}')" IFS=":" read -ra a_path_loc <<< "$l_root_path" grep -q -- "::" <<< "$l_root_path" && \ a_output2+=(" - root's path contains a empty directory (::)") grep -Pq -- ":\h*$" <<< "$l_root_path" && \ a_output2+=(" - root's path contains a trailing (:)") grep -Pq -- '(^\h*|:)\.(:|\h*$)' <<< "$l_root_path" && \ a_output2+=(" - root's path contains current working directory (.)") for l_path in "${a_path_loc[@]}"; do if [ -d "$l_path" ]; then while IFS=: read -r l_fmode l_fown; do [ "$l_fown" != "root" ] && \ a_output2+=(" - Directory: \"$l_path\" is owned by: \"$l_fown\"" \ " should be owned by \"root\"") [ $(( $l_fmode & $l_pmask )) -gt 0 ] && \ a_output2+=(" - Directory: \"$l_path\" is mode: \"$l_fmode\"" \ " and should be mode: \"$l_maxperm\" or more restrictive") done <<< "$(stat -Lc '%#a:%U' "$l_path")" else a_output2+=(" - \"$l_path\" is not a directory") fi done if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" \ " - Root's path is correctly configured" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" \ "- * Reasons for audit failure * :" "${a_output2[@]}" fi } Page 644 Internal Only - General Remediation: Correct or justify any: • Locations that are not directories • Empty directories (::) • Trailing (:) • Current working directory (.) • Non root owned directories • Directories that less restrictive than mode 0755 References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 645 Internal Only - General 5.4.2.6 Ensure root user umask is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user file-creation mode mask (umask) is used to determine the file permission for newly created directories and files. In Linux, the default permissions for any newly created directory is 0777 (rwxrwxrwx), and for any newly created file it is 0666 (rw-rw- rw-). The umask modifies the default Linux permissions by restricting (masking) these permissions. The umask is not simply subtracted, but is processed bitwise. Bits set in the umask are cleared in the resulting file mode. umask can be set with either Octal or Symbolic values: • Octal (Numeric) Value - Represented by either three or four digits. ie umask 0027 or umask 027. If a four digit umask is used, the first digit is ignored. The remaining three digits effect the resulting permissions for user, group, and world/other respectively. • Symbolic Value - Represented by a comma separated list for User u, group g, and world/other o. The permissions listed are not masked by umask. ie a umask set by umask u=rwx,g=rx,o= is the Symbolic equivalent of the Octal umask 027. This umask would set a newly created directory with file mode drwxr-x--- and a newly created file with file mode rw-r-----. root user Shell Configuration Files: • /root/.profile - Is executed to configure the root users' shell before the initial command prompt. Is only read by login shells. • /root/.bashrc - Is executed for interactive shells. only read by a shell that's both interactive and non-login umask is set by order of precedence. If umask is set in multiple locations, this order of precedence will determine the system's default umask. Order of precedence: 1. /root/.profile 2. /root/.bashrc 3. The system default umask Page 646 Internal Only - General Rationale: Setting a secure value for umask ensures that users make a conscious choice about their file permissions. A permissive umask value could result in directories or files with excessive permissions that can be read and/or written to by unauthorized users. Audit: Run the following command to verify that the root user files, /root/.profile and /root/.bashrc, do not include a umask that is less restrictive than 0027: # grep -Psi -- '^\h*umask\h+((\d{1,2}(\d[^7]|[^2- 7]\d)\b)|(u=[rwx]{1,3},)?(((g=[rx]?[rx]?w[rx]?[rx]?\b)(,o=[rwx]{1,3})?)|((g=[ wrx]{1,3},)?o=[wrx]{1,3}\b)))' /root/.profile /root/.bashrc Nothing should be returned. Remediation: Edit /root/.profile and /root/.bashrc and either: • remove, comment out, or update any line with umask. - OR - • update any line that includes umask to a value of 0027 or more restrictive. Example: umask 027 Note: the Recommendation "Ensure default user umask is configured" includes guidance to set the default umask Default Value: System default umask References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 647 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 648 Internal Only - General 5.4.2.7 Ensure system accounts do not have a valid login shell (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of accounts provided with most distributions that are used to manage applications and are not intended to provide an interactive shell. Furthermore, a user may add special accounts that are not intended to provide an interactive shell. Rationale: It is important to make sure that accounts that are not being used by regular users are prevented from being used to provide an interactive shell. By default, most distributions set the password field for these accounts to an invalid string, but it is also recommended that the shell field in the password file be set to the nologin shell. This prevents the account from potentially being used to run any commands. Audit: Run the following command to verify system accounts, except for root, halt, sync, shutdown or nfsnobody, do not have a valid login shell: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 == 65534) && $(NF) ~ pat) {print "Service account: \"" $1 "\" has a valid shell: " $7}' /etc/passwd } Nothing should be returned Page 649 Internal Only - General Remediation: Run the following command to set the shell for any service accounts returned by the audit to nologin: # usermod -s $(command -v nologin) Example script: #!/usr/bin/env bash { l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" awk -v pat="$l_valid_shells" -F: '($1!~/^(root|halt|sync|shutdown|nfsnobody)$/ && ($3<'"$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs)"' || $3 == 65534) && $(NF) ~ pat) {system ("usermod -s '"$(command -v nologin)"' " $1)}' /etc/passwd } References: 1. NIST SP 800-53 Rev. 5: AC-2(5), AC-3, AC-11, MP-2 Additional Information: The root, sync, shutdown, and halt users are exempted from requiring a non-login shell. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 650 Internal Only - General 5.4.2.8 Ensure accounts without a valid login shell are locked (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: There are a number of accounts provided with most distributions that are used to manage applications and are not intended to provide an interactive shell. Furthermore, a user may add special accounts that are not intended to provide an interactive shell. Rationale: It is important to make sure that accounts that are not being used by regular users are prevented from being used to provide an interactive shell. By default, most distributions set the password field for these accounts to an invalid string, but it is also recommended that the shell field in the password file be set to the nologin shell. This prevents the account from potentially being used to run any commands. Audit: Run the following script to verify all non-root accounts without a valid login shell are locked. #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" while IFS= read -r l_user; do passwd -S "$l_user" | awk '$2 !~ /^L/ {print "Account: \"" $1 "\" does not have a valid login shell and is not locked"}' done < <(awk -v pat="$l_valid_shells" -F: '($1 != "root" && $(NF) !~ pat) {print $1}' /etc/passwd) } Nothing should be returned Page 651 Internal Only - General Remediation: Run the following command to lock any non-root accounts without a valid login shell returned by the audit: # usermod -L Example script: #!/usr/bin/env bash { l_valid_shells="^($(awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" while IFS= read -r l_user; do passwd -S "$l_user" | awk '$2 !~ /^L/ {system ("usermod -L " $1)}' done < <(awk -v pat="$l_valid_shells" -F: '($1 != "root" && $(NF) !~ pat) {print $1}' /etc/passwd) } References: 1. NIST SP 800-53 Rev. 5: AC-2(5), AC-3, AC-11, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 652 Internal Only - General 5.4.3 Configure user default environment Page 653 Internal Only - General 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: /etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh and available to be queried by other programs. Be aware that there are programs which consult this file to find out if a user is a normal user; for example, FTP daemons traditionally disallow access to users with shells not included in this file. Rationale: A user can use chsh to change their configured shell. If a user has a shell configured that isn't in in /etc/shells, then the system assumes that they're somehow restricted. In the case of chsh it means that the user cannot change that value. Other programs might query that list and apply similar restrictions. By putting nologin in /etc/shells, any user that has nologin as its shell is considered a full, unrestricted user. This is not the expected behavior for nologin. Audit: Run the following command to verify that nologin is not listed in the /etc/shells file: # grep -Ps '^\h*([^#\n\r]+)?\/nologin\b' /etc/shells Nothing should be returned Remediation: Edit /etc/shells and remove any lines that include nologin References: 1. shells(5) 2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 654 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 655 Internal Only - General 5.4.3.2 Ensure default user shell timeout is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: TMOUT is an environmental setting that determines the timeout of a shell in seconds. • TMOUT=n - Sets the shell timeout to n seconds. A setting of TMOUT=0 disables timeout. • readonly TMOUT- Sets the TMOUT environmental variable as readonly, preventing unwanted modification during run-time. • export TMOUT - exports the TMOUT variable System Wide Shell Configuration Files: • /etc/profile - used to set system wide environmental variables on users shells. The variables are sometimes the same ones that are in the .bash_profile, however this file is used to set an initial PATH or PS1 for all shell users of the system. is only executed for interactive login shells, or shells executed with the --login parameter. • /etc/profile.d - /etc/profile will execute the scripts within /etc/profile.d/*.sh. It is recommended to place your configuration in a shell script within /etc/profile.d to set your own system wide environmental variables. • /etc/bash.bashrc - System wide version of .bashrc. In Fedora derived distributions, /etc/bashrc also invokes /etc/profile.d/*.sh if non-login shell, but redirects output to /dev/null if non-interactive. Is only executed for interactive shells or if BASH_ENV is set to /etc/bash.bashrc. Rationale: Setting a timeout value reduces the window of opportunity for unauthorized user access to another user's shell session that has been left unattended. It also ends the inactive session and releases the resources associated with that session. Audit: Run the following script to verify that TMOUT is configured to: include a timeout of no more than 900 seconds, to be readonly, to be exported, and is not being changed to a longer timeout. Page 656 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=(); l_tmout_set="900" f_tmout_read_chk() { a_out=(); a_out2=() l_tmout_readonly="$(grep -P -- '^\h*(typeset\h\- xr\hTMOUT=\d+|([^#\n\r]+)?\breadonly\h+TMOUT\b)' "$l_file")" l_tmout_export="$(grep -P -- '^\h*(typeset\h\- xr\hTMOUT=\d+|([^#\n\r]+)?\bexport\b([^#\n\r]+\b)?TMOUT\b)' "$l_file")" if [ -n "$l_tmout_readonly" ]; then a_out+=(" - Readonly is set as: \"$l_tmout_readonly\" in: \"$l_file\"") else a_out2+=(" - Readonly is not set in: \"$l_file\"") fi if [ -n "$l_tmout_export" ]; then a_out+=(" - Export is set as: \"$l_tmout_export\" in: \"$l_file\"") else a_out2+=(" - Export is not set in: \"$l_file\"") fi } while IFS= read -r l_file; do l_tmout_value="$(grep -Po -- '^([^#\n\r]+)?\bTMOUT=\d+\b' "$l_file" | awk -F= '{print $2}')" f_tmout_read_chk if [ -n "$l_tmout_value" ]; then if [[ "$l_tmout_value" -le "$l_tmout_set" && "$l_tmout_value" -gt "0" ]]; then a_output+=(" - TMOUT is set to: \"$l_tmout_value\" in: \"$l_file\"") [ "${#a_out[@]}" -gt 0 ] && a_output+=("${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=("${a_out[@]}") fi if [[ "$l_tmout_value" -gt "$l_tmout_set" || "$l_tmout_value" -le "0" ]]; then a_output2+=(" - TMOUT is incorrectly set to: \"$l_tmout_value\" in: \"$l_file\"") [ "${#a_out[@]}" -gt 0 ] && a_output2+=(" ** Incorrect TMOUT value **" "${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=("${a_out2[@]}") fi else [ "${#a_out[@]}" -gt 0 ] && a_output2+=(" - TMOUT is not set" "${a_out[@]}") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - TMOUT is not set" "${a_out2[@]}") fi done < <(grep -Pls -- '^([^#\n\r]+)?\bTMOUT\b' /etc/*bashrc /etc/profile /etc/profile.d/*.sh) [[ "${#a_output[@]}" -le 0 && "${#a_output2[@]}" -le 0 ]] && a_output2+=(" - TMOUT is not configured") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 657 Internal Only - General Note: If TMOUT is set as readonly through readonly TMOUT and/or typeset -xr in more than once, you will receive an error message when logging into a terminal session or connecting with openSSH. It is recommended that TMOUT be set only once in only one file. Remediation: Review /etc/bashrc, /etc/profile, and all files ending in *.sh in the /etc/profile.d/ directory and remove or edit all TMOUT=_n_ entries to follow local site policy. TMOUT should not exceed 900 or be equal to 0. Configure TMOUT in one of the following files: • A file in the /etc/profile.d/ directory ending in .sh • /etc/profile • /etc/bashrc Example command to set TMOUT to 900 seconds in a file in /etc/profile.d/: # printf '%s\n' "# Set TMOUT to 900 seconds" "typeset -xr TMOUT=900" > /etc/profile.d/50-tmout.sh TMOUT configuration examples: typeset -xr TMOUT=900 Deprecated methods: • As multiple lines: TMOUT=900 readonly TMOUT export TMOUT • As a single line: readonly TMOUT=900 ; export TMOUT Additional Information: The audit and remediation in this recommendation apply to bash and shell. If other shells are supported on the system, it is recommended that their configuration files also are checked. Other methods of setting a timeout exist for other shells not covered here. Ensure that the timeout conforms to your local policy. Page 658 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.3 Configure Automatic Session Locking on Enterprise Assets v8 Configure automatic session locking on enterprise assets after a defined period ● ● ● of inactivity. For general purpose operating systems, the period must not exceed 15 minutes. For mobile end-user devices, the period must not exceed 2 minutes. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. Page 659 Internal Only - General 5.4.3.3 Ensure default user umask is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user file-creation mode mask (umask) is used to determine the file permission for newly created directories and files. In Linux, the default permissions for any newly created directory is 0777 (rwxrwxrwx), and for any newly created file it is 0666 (rw-rw- rw-). The umask modifies the default Linux permissions by restricting (masking) these permissions. The umask is not simply subtracted, but is processed bitwise. Bits set in the umask are cleared in the resulting file mode. umask can be set with either Octal or Symbolic values: • Octal (Numeric) Value - Represented by either three or four digits. ie umask 0027 or umask 027. If a four digit umask is used, the first digit is ignored. The remaining three digits effect the resulting permissions for user, group, and world/other respectively. • Symbolic Value - Represented by a comma separated list for User u, group g, and world/other o. The permissions listed are not masked by umask. ie a umask set by umask u=rwx,g=rx,o= is the Symbolic equivalent of the Octal umask 027. This umask would set a newly created directory with file mode drwxr-x--- and a newly created file with file mode rw-r-----. The default umask can be set to use the pam_umask module or in a System Wide Shell Configuration File. The user creating the directories or files has the discretion of changing the permissions via the chmod command, or choosing a different default umask by adding the umask command into a User Shell Configuration File, ( .bash_profile or .bashrc), in their home directory. Setting the default umask: • pam_umask module: o will set the umask according to the system default in /etc/login.defs and user settings, solving the problem of different umask settings with different shells, display managers, remote sessions etc. o umask= value in the /etc/login.defs file is interpreted as Octal o Setting USERGROUPS_ENAB to yes in /etc/login.defs (default): ▪ will enable setting of the umask group bits to be the same as owner bits. (examples: 022 -> 002, 077 -> 007) for non-root users, if the uid is the same as gid, and username is the same as the Page 660 Internal Only - General ▪ userdel will remove the user's group if it contains no more members, and useradd will create by default a group with the name of the user • System Wide Shell Configuration File: o /etc/profile - used to set system wide environmental variables on users shells. The variables are sometimes the same ones that are in the .bash_profile, however this file is used to set an initial PATH or PS1 for all shell users of the system. is only executed for interactive login shells, or shells executed with the --login parameter. o /etc/profile.d - /etc/profile will execute the scripts within /etc/profile.d/*.sh. It is recommended to place your configuration in a shell script within /etc/profile.d to set your own system wide environmental variables. o /etc/bashrc - System wide version of .bashrc. In Fedora derived distributions, etc/bashrc also invokes /etc/profile.d/*.sh if non-login shell, but redirects output to /dev/null if non-interactive. Is only executed for interactive shells or if BASH_ENV is set to /etc/bashrc. User Shell Configuration Files: • ~/.bash_profile - Is executed to configure your shell before the initial command prompt. Is only read by login shells. • ~/.bashrc - Is executed for interactive shells. only read by a shell that's both interactive and non-login umask is set by order of precedence. If umask is set in multiple locations, this order of precedence will determine the system's default umask. Order of precedence: 1. A file in /etc/profile.d/ ending in .sh - This will override any other system- wide umask setting 2. In the file /etc/profile 3. On the pam_umask.so module in /etc/pam.d/postlogin 4. In the file /etc/login.defs 5. In the file /etc/default/login Rationale: Setting a secure default value for umask ensures that users make a conscious choice about their file permissions. A permissive umask value could result in directories or files with excessive permissions that can be read and/or written to by unauthorized users. Satisfies: SRG-OS-000480-GPOS-00228, SRG-OS-000480-GPOS-00227 Page 661 Internal Only - General Audit: Run the following commands to verify the systemwide umask is 0027 (u=rwx,g=rx,o=) or more restrictive: 1. Run the following command to verify umask is set to 027 or more restrictive in a file ending in .sh in /etc/profile.d/ # grep -Psi -- '^\h*umask\b' /etc/profile.d/*.sh Example output: umask 027 2. Run the following command to verify UMASK is 027 or more restrictive in /etc/login.defs: # grep -Psi -- '^\h*UMASK\b' /etc/login.defs Example output: UMASK 027 Remediation: 1. Run the following script to comment out all occurrences of umask that are less restrictive than 027 in files ending in *.sh in the /etc/profile.d/ directory: #!/usr/bin/env bash { while IFS= read -r -d $'\0' l_file; do sed -ri '/^\s*umask\s+0?(0[01][0-7]|0[0-7][^7]|[^0][0-7][0- 7])(\s*|\s+.*)$/s/^/# /' "$l_file" done < <(find /etc/profile.d/ -type f -name '*.sh' -print0) } 2. Create or edit a file in /etc/profile.d/ ending in *.sh and add or modify the following line: umask 0027 Example: # printf '%s\n' "" "umask 027" >> /etc/profile.d/60-default_umask.sh 3. Edit /etc/login.defs and add or update the following line: UMASK 027 Notes: • This method only applies to bash and shell. If other shells are supported on the system, it is recommended that their configuration files also are checked • If the pam_umask.so module is going to be used to set umask, ensure that it's not being overridden by another setting. Refer to the PAM_UMASK(8) man page for more information Page 662 Internal Only - General Default Value: UMASK 022 References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-020351 | RULE ID: SV-230383r1017192 | CAT II 5. STIG ID: RHEL-08-020353 | RULE ID: SV-230385r1017194 | CAT II 6. STIG ID: RHEL-09-412055 | RULE ID: SV-258072r1045155 | CAT II 7. STIG ID: RHEL-09-412065 | RULE ID: SV-258074r991590 | CAT II 8. STIG ID: RHEL-09-412070 | RULE ID: SV-258075r991590 | CAT II 9. STIG ID: ALMA-09-017620 | RULE ID: SV-269235r1050117 | CAT II 10. STIG ID: ALMA-09-017840 | RULE ID: SV-269237r1050119 | CAT II 11. STIG ID: UBTU-22-412035 | RULE ID: SV-260555r991590 | CAT II 12. STIG ID: UBTU-24-300030 | RULE ID: SV-270716r1066637 | CAT II 13. STIG ID: SLES-15-040420 | RULE ID: SV-235030r991590 | CAT II Additional Information: • Other methods of setting a default user umask exist • If other methods are in use in your environment they should be audited • The default user umask can be overridden with a user specific umask • The user creating the directories or files has the discretion of changing the permissions: o Using the chmod command o Setting a different default umask by adding the umask command into a User Shell Configuration File, (.bashrc), in their home directory o Manually changing the umask for the duration of a login session by running the umask command CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 663 Internal Only - General 6 Logging and Auditing The items in this section describe how to configure logging, log monitoring, and auditing, using tools included in most distributions. It is recommended that rsyslog be used for logging (with logwatch providing summarization) and auditd be used for auditing (with aureport providing summarization) to automatically monitor logs for intrusion attempts and other suspicious system behavior. In addition to the local log files created by the steps in this section, it is also recommended that sites collect copies of their system logs on a secure, centralized log server via an encrypted connection. Not only does centralized logging help sites correlate events that may be occurring on multiple systems, but having a second copy of the system log information may be critical after a system compromise where the attacker has modified the local log files on the affected system(s). If a log correlation system is deployed, configure it to process the logs described in this section. Because it is often necessary to correlate log information from many different systems (particularly after a security incident) it is recommended that the time be synchronized among systems and devices connected to the local network. The standard Internet protocol for time synchronization is the Network Time Protocol (NTP), which is supported by most network-ready devices. Reference manual page for more information on configuring chrony. It is important that all logs described in this section be monitored on a regular basis and correlated to determine trends. A seemingly innocuous entry in one log could be more significant when compared to an entry in another log. Note on log file permissions: There really isn't a "one size fits all" solution to the permissions on log files. Many sites utilize group permissions so that administrators who are in a defined security group, such as "wheel" do not have to elevate privileges to root in order to read log files. Also, if a third party log aggregation tool is used, it may need to have group permissions to read the log files, which is preferable to having it run setuid to root. Therefore, there are two remediation and audit steps for log file permissions. One is for systems that do not have a secured group method implemented that only permits root to read the log files (root:root 600). The other is for sites that do have such a setup and are designated as root:securegrp 640 where securegrp is the defined security group (in some cases wheel). Page 664 Internal Only - General 6.1 System Logging Logging services should be configured to prevent information leaks and to aggregate logs on a remote server so that they can be reviewed in the event of a system compromise. A centralized log server provides a single point of entry for further analysis, monitoring and filtering. Security principals for logging • Ensure transport layer security is implemented between the client and the log server. • Ensure that logs are rotated as per the environment requirements. • Ensure all locally generated logs have the appropriate permissions. • Ensure all security logs are sent to a remote log server. • Ensure the required events are logged. What is covered This section will cover the minimum best practices for the usage of either rsyslog or journald. The recommendations are written such that each is wholly independent of each other and only one is implemented. • If your organization makes use of an enterprise wide logging system completely outside of rsyslog or journald, then the following recommendations do not directly apply. However, the principals of the recommendations should be followed regardless of what solution is implemented. If the enterprise solution incorporates either of these tools, careful consideration should be given to the following recommendations to determine exactly what applies. • Should your organization make use of both rsyslog and journald, take care how the recommendations may or may not apply to you. What is not covered • Enterprise logging systems not utilizing rsyslog or journald. As logging is very situational and dependent on the local environment, not everything can be covered here. • Transport layer security should be applied to all remote logging functionality. Both rsyslog and journald supports secure transport and should be configured as such. • The log server. There are a multitude of reasons for a centralized log server (and keeping a short period of logging on the local system), but the log server is out of scope for these recommendations. Page 665 Internal Only - General 6.1.1 Configure journald Included in the systemd suite is a journaling service called systemd- journald.service for the collection and storage of logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources such as: • Classic RFC3164 BSD syslog via the /dev/log socket • STDOUT/STDERR of programs via StandardOutput=journal + StandardError=journal in service files (both of which are default settings) • Kernel log messages via the /dev/kmsg device node • Audit records via the kernel’s audit subsystem • Structured log messages via journald’s native protocol Any changes made to the systemd-journald configuration will require a re-start of systemd-journald Page 666 Internal Only - General 6.1.1.1 Configure systemd-journald service systemd-journald is a system service that collects and stores logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources: • Kernel log messages, via kmsg • Simple system log messages, via the libc syslog call • Structured system log messages via the native Journal API • Standard output and standard error of service units • Audit records, originating from the kernel audit subsystem The daemon will implicitly collect numerous metadata fields for each log messages in a secure and unfakeable way. See systemd.journal-fields man page for more information about the collected metadata. The journal service stores log data either persistently below /var/log/journal or in a volatile way below /run/log/journal/. By default, log data is stored persistently if /var/log/journal/ exists during boot, with an implicit fallback to volatile storage. Use Storage= in journald.conf to configure where log data is placed, independently of the existence of /var/log/journal/. On systems where /var/log/journal/ does not exist but where persistent logging is desired, and the default journald.conf is used, it is sufficient to create the directory and ensure it has the correct access modes and ownership. Page 667 Internal Only - General 6.1.1.1.1 Ensure journald service is active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Ensure that the systemd-journald service is enabled to allow capturing of logging events. Rationale: If the systemd-journald service is not enabled to start on boot, the system will not capture logging events. Audit: Run the following command to verify systemd-journald is active: # systemctl is-active systemd-journald.service active Remediation: Run the following commands to unmask, enable, and start systemd- journald.service # systemctl unmask systemd-journald.service # systemctl --now enable systemd-journald.service References: 1. CCI-001665 2. NIST SP 800-53 :: SC-24 3. NIST SP 800-53A :: SC-24.1 (v) 4. STIG ID: RHEL-09-211040 | RULE ID: SV-257783r991562 | CAT II 5. STIG ID: ALMA-09-041490 | RULE ID: SV-269428r1050311 | CAT II 6. STIG ID: OL09-00-002400 | RULE ID: SV-271739r1091929 | CAT II Page 668 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 669 Internal Only - General 6.1.1.1.2 Ensure journald log file access is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald will create logfiles that do not already exist on the system. This setting controls what permissions will be applied to these newly created files. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected. Page 670 Internal Only - General Audit: First determine if there is an override file /etc/tmpfiles.d/systemd.conf. If so, this file will override all default settings as defined in /usr/lib/tmpfiles.d/systemd.conf and should be inspected. If no override file exists, inspect the default /usr/lib/tmpfiles.d/systemd.conf against the site specific requirements. Ensure that file permissions are mode 0640 or more restrictive. Run the following script to verify if an override file exists or not and if the files permissions are mode 0640 or more restrictive: #!/usr/bin/env bash { config_files=(/etc/tmpfiles.d/systemd.conf /usr/lib/tmpfiles.d/systemd.conf) warn=() for file in "${config_files[@]}"; do [ -f "$file" ] || continue while read -r type path perm _; do if [[ "$type" == "f" && "$perm" =~ ^0?[0-7]{3,4}$ ]]; then perm="${perm#0}" if [ -f "$path" ]; then actual=$(stat -c "%a" "$path" 2>/dev/null) if [[ -n "$actual" && "$actual" -gt 640 ]]; then warn+=("File: $path | Perm: $actual (expected max: 640) | Defined in: $file") fi fi fi done < "$file" done if [ "${#warn[@]}" -eq 0 ]; then echo "No files with permissions more permissive than 0640." else echo -e " *** REVIEW ***" printf "%s\n" "${warn[@]}" fi } Remediation: If the default configuration is not appropriate for the site specific requirements, copy /usr/lib/tmpfiles.d/systemd.conf to /etc/tmpfiles.d/systemd.conf and modify as required. Requirements is either 0640 or site policy if that is less restrictive. References: 1. NIST SP 800-53 Rev. 5: AC-3, AU-2, AU-12, MP-2, SI-5 Page 671 Internal Only - General Additional Information: See man 5 tmpfiles.d for detailed information on the permission sets for the relevant log files. Further information with examples can be found at https://www.freedesktop.org/software/systemd/man/tmpfiles.d.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 672 Internal Only - General 6.1.1.1.3 Ensure journald log file rotation is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald includes the capability of rotating log files regularly to avoid filling up the system with logs or making the logs unmanageably large. The file /etc/systemd/journald.conf is the configuration file used to specify how logs generated by Journald should be rotated. Rationale: By keeping the log files smaller and more manageable, a system administrator can easily archive these files to another system and spend less time looking through inordinately large log files. Audit: Review /etc/systemd/journald.conf and files in the /etc/systemd/journald.conf.d/ directory ending in .conf. Verify logs are rotated according to site policy. Run the following command and ensure logs are rotated according to site policy: # systemd-analyze cat-config systemd/journald.conf | tac | \ grep -Psi -- '\b(SystemMaxUse|SystemKeepFree|RuntimeMaxUse|RuntimeKeepFree|MaxFileSec)=' SystemMaxUse= SystemKeepFree= RuntimeMaxUse= RuntimeKeepFree= MaxFileSec= Page 673 Internal Only - General Remediation: Edit /etc/systemd/journald.conf or a file ending in .conf the /etc/systemd/journald.conf.d/ directory. Set the following parameters in the [Journal] section to ensure logs are rotated according to site policy. The settings should be carefully understood as there are specific edge cases and prioritization of parameters. Example Configuration [Journal] SystemMaxUse=1G SystemKeepFree=500M RuntimeMaxUse=200M RuntimeKeepFree=50M MaxFileSec=1month Note: If these settings appear in a canonically later file, or later in the same file, the setting will be overwritten References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12 2. https://man7.org/linux/man-pages/man5/journald.conf.5.html Additional Information: See man 5 journald.conf for detailed information regarding the parameters in use. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 674 Internal Only - General 6.1.1.1.4 Ensure journald ForwardToSyslog is disabled (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from journald should be kept in the confines of the service and not forwarded to other services. Rationale: - IF - journald is the method for capturing logs, all logs of the system should be handled by journald and not forwarded to other logging mechanisms. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Page 675 Internal Only - General Audit: - IF - journald is the method for capturing logs Run the following script to verify ForwardToSyslog in not set to yes: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="ForwardToSyslog" l_option_value="no" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 676 Internal Only - General Remediation: - IF - rsyslog is the preferred method for capturing logs, this section and Recommendation should be skipped and the "Configure rsyslog" section followed. - IF - journald is the preferred method for capturing logs: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: ForwardToSyslog=no Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "" "ForwardToSyslog=no" >> /etc/systemd/journald.conf.d/60-journald.conf else printf '%s\n' "" "[Journal]" "ForwardToSyslog=no" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald Default Value: ForwardToSyslog=no References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-6, AU-7, AU-12 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html Page 677 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 678 Internal Only - General 6.1.1.1.5 Ensure journald Storage is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from journald may be stored in volatile memory or persisted locally on the server. Logs in memory will be lost upon a system reboot. By persisting logs to local disk on the server they are protected from loss due to a reboot. Rationale: Writing log data to disk will provide the ability to forensically reconstruct events which may have impacted the operations or security of a system even after a system crash or reboot. Page 679 Internal Only - General Audit: Run the following script to verify Storage is set to persistent: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="Storage" l_option_value="persistent" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 680 Internal Only - General Remediation: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: Storage=persistent Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "Storage=persistent" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "" "[Journal]" "Storage=persistent" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-12 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html Page 681 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 682 Internal Only - General 6.1.1.1.6 Ensure journald Compress is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The journald system includes the capability of compressing overly large files to avoid filling up the system with logs or making the logs unmanageably large. Rationale: Uncompressed large files may unexpectedly fill a filesystem leading to resource unavailability. Compressing logs prior to write can prevent sudden, unexpected filesystem impacts. Page 683 Internal Only - General Audit: Run the following script to verify Compress is set to yes: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="Compress" l_option_value="yes" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="$(readlink -e /etc/"$l_conf_file" || \ readlink -e /usr/lib/"$l_conf_file")" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Page 684 Internal Only - General Remediation: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: Compress=yes Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir -p /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\]' /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "" "Compress=yes" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "" "[Journal]" "Compress=yes" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: # systemctl reload-or-restart systemd-journald References: 1. NIST SP 800-53 Rev. 5: AU-4 2. journald.conf(5) - Linux manual page: https://man7.org/linux/man- pages/man5/journald.conf.5.html Page 685 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 686 Internal Only - General 6.1.1.2 Configure systemd-journal-remote The systemd-journal-remote package includes systemd-journal-upload. systemd-journal-upload will upload journal entries to the URL specified with --url=. This program reads journal entries from one or more journal files, similarly to journalctl. systemd-journal-upload transfers the raw content of journal file and uses HTTP as a transport protocol. systemd-journal-upload.service is a system service that uses systemd-journal- upload to upload journal entries to a server. It uses the configuration in journal- upload.conf. Page 687 Internal Only - General 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-remote supports the ability to send log events it gathers to a remote log host or to receive messages from remote hosts, thus enabling centralized log management. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Audit: - IF - journald will be used for logging on the system: Run the following command to verify systemd-journal-remote is installed. # dpkg-query -s systemd-journal-remote &>/dev/null && echo "systemd-journal- remote is installed" Verify the output matches: systemd-journal-remote is installed Remediation: Run the following command to install systemd-journal-remote: # apt install systemd-journal-remote References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7 AU-12 Page 688 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 689 Internal Only - General 6.1.1.2.2 Ensure systemd-journal-upload authentication is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-upload supports the ability to send log events it gathers to a remote log host. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Page 690 Internal Only - General Audit: Run the following script to verify systemd-journal-upload authentication is configured: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journal-upload.conf" l_block="Upload" while IFS= read -r l_file; do l_file="${l_file//# /}" gawk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi -- \ '^\h*(URL|ServerKeyFile|ServerCertificateFile|TrustedCertificateFile)\h*=\h*\ H+\b' done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') } Verify the output matches per your environments certificate locations and the URL of the log server: Example output: URL=192.168.50.42 ServerKeyFile=/etc/ssl/private/journal-upload.pem ServerCertificateFile=/etc/ssl/certs/journal-upload.pem TrustedCertificateFile=/etc/ssl/ca/trusted.pem Page 691 Internal Only - General Remediation: Edit the /etc/systemd/journal-upload.conf file or a file in /etc/systemd/journal-upload.conf.d ending in .conf and ensure the following lines are set in the [Upload] section per your environment: [Upload] URL=192.168.50.42 ServerKeyFile=/etc/ssl/private/journal-upload.pem ServerCertificateFile=/etc/ssl/certs/journal-upload.pem TrustedCertificateFile=/etc/ssl/ca/trusted.pem Example script: #!/usr/bin/env bash { [ ! -d "/etc/systemd/journal-upload.conf.d" ] && \ mkdir -p /etc/systemd/journal-upload.conf.d printf '%s\n' "" "[Upload]" "URL=192.168.50.42" \ "ServerKeyFile=/etc/ssl/private/journal-upload.pem" \ "ServerCertificateFile=/etc/ssl/certs/journal-upload.pem" \ "TrustedCertificateFile=/etc/ssl/ca/trusted.pem" \ >> /etc/systemd/journal-upload.conf.d/60-journal-upload.conf } Restart the service: # systemctl reload-or-restart systemd-journal-upload References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 692 Internal Only - General 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-upload supports the ability to send log events it gathers to a remote log host. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Audit: Run the following command to verify systemd-journal-upload is enabled. # systemctl is-enabled systemd-journal-upload.service enabled Run the following command to verify systemd-journal-upload is active: # systemctl is-active systemd-journal-upload.service active Remediation: Run the following commands to unmask, enable and start systemd-journal-upload: # systemctl unmask systemd-journal-upload.service # systemctl --now enable systemd-journal-upload.service References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12 Page 693 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 694 Internal Only - General 6.1.1.2.4 Ensure systemd-journal-remote service is not in use (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Journald systemd-journal-remote supports the ability to receive messages from remote hosts, thus acting as a log server. Clients should not receive data from other hosts. Note: • The same package, systemd-journal-remote, is used for both sending logs to remote hosts and receiving incoming logs. • With regards to receiving logs, there are two services; systemd-journal- remote.socket and systemd-journal-remote.service. Rationale: If a client is configured to also receive data, thus turning it into a server, the client system is acting outside it's operational boundary. Note: This recommendation only applies if journald is the chosen method for client side logging. Do not apply this recommendation if rsyslog is used. Audit: Run the following command to verify systemd-journal-remote.socket and systemd- journal-remote.service are not enabled: # systemctl is-enabled systemd-journal-remote.socket systemd-journal- remote.service | grep -P -- '^enabled' Nothing should be returned Run the following command to verify systemd-journal-remote.socket and systemd- journal-remote.service are not active: # systemctl is-active systemd-journal-remote.socket systemd-journal- remote.service | grep -P -- '^active' Nothing should be returned Page 695 Internal Only - General Remediation: Run the following commands to stop and mask systemd-journal-remote.socket and systemd-journal-remote.service: # systemctl stop systemd-journal-remote.socket systemd-journal-remote.service # systemctl mask systemd-journal-remote.socket systemd-journal-remote.service References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7 AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 696 Internal Only - General 6.1.2 Configure rsyslog The rsyslog software package may be used instead of the default journald logging mechanism. Rsyslog has evolved over several decades. For this reason it supports three different configuration formats (“languages”): • basic - previously known as the sysklogd format, this is the format best used to express basic things, such as where the statement fits on a single line. o It stems back to the original syslog.conf format, in use now for several decades. o The most common use case is matching on facility/severity and writing matching messages to a log file. • advanced - previously known as the RainerScript format, this format was first available in rsyslog v6 and is the current, best and most precise format for non- trivial use cases where more than one line is needed. o Prior to v7, there was a performance impact when using this format that encouraged use of the basic format for best results. Current versions of rsyslog do not suffer from this (historical) performance impact. o This new style format is specifically targeted towards more advanced use cases like forwarding to remote hosts that might be partially offline. • obsolete legacy - previously known simply as the legacy format, this format is exactly what its name implies: it is obsolete and should not be used when writing new configurations. It was created in the early days (up to rsyslog version 5) where we expected that rsyslog would extend sysklogd just mildly. Consequently, it was primarily aimed at small additions to the original sysklogd format. o Practice has shown that it was notoriously hard to use for more advanced use cases, and thus we replaced it with the advanced format. o In essence, everything that needs to be written on a single line that starts with a dollar sign is legacy format. Users of this format are encouraged to migrate to the basic or advanced formats. Note: This section only applies if rsyslog is the chosen method for client side logging. Do not apply this section if journald is used. Page 697 Internal Only - General 6.1.2.1 Ensure rsyslog is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The rsyslog software is recommended in environments where journald does not meet operation requirements. Rationale: The security enhancements of rsyslog such as connection-oriented (i.e. TCP) transmission of logs, the option to log to database formats, and the encryption of log data en route to a central logging server) justify installing and configuring the package. Audit: - IF - rsyslog is being used for logging on the system: Run the following command to verify rsyslog is installed: # dpkg-query -s rsyslog &>/dev/null && echo "rsyslog is installed" Verify the output matches: rsyslog is installed Remediation: Run the following command to install rsyslog: # apt install rsyslog Default Value: Installed References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 Page 698 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 699 Internal Only - General 6.1.2.2 Ensure rsyslog service is enabled and active (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Once the rsyslog package is installed, ensure that the service is enabled. Rationale: If the rsyslog service is not enabled to start on boot, the system will not capture logging events. Audit: - IF - rsyslog is being used for logging on the system: Run the following command to verify rsyslog.service is enabled: # systemctl is-enabled rsyslog enabled Run the following command to verify rsyslog.service is active: # systemctl is-active rsyslog.service active Remediation: - IF - rsyslog is being used for logging on the system: Run the following commands to unmask, enable, and start rsyslog.service: # systemctl unmask rsyslog.service # systemctl enable rsyslog.service # systemctl start rsyslog.service References: 1. CCI-000366 2. NIST SP 800-53 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) 4. STIG ID: RHEL-08-010561 | RULE ID: SV-230298r1017108 | CAT II 5. STIG ID: OL08-00-010561 | RULE ID: SV-248615r991589 | CAT II 6. STIG ID: ALMA-09-053150 | RULE ID: SV-269518r1050401 | CAT II 7. STIG ID: UBTU-22-652010 | RULE ID: SV-260588r991562 | CAT II Page 700 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 701 Internal Only - General 6.1.2.3 Ensure journald is configured to send logs to rsyslog (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Data from systemd-journald may be stored in volatile memory or persisted locally on the server. Utilities exist to accept remote export of systemd-journald logs, however, use of the rsyslog service provides a consistent means of log collection and export. Rationale: - IF - rsyslog is the preferred method for capturing logs, all logs of the system should be sent to it for further processing. Note: This recommendation only applies if rsyslog is the chosen method for client side logging. Do not apply this recommendation if systemd-journald is used. Page 702 Internal Only - General Audit: - IF - rsyslog is the preferred method for capturing logs Run the following script to verify that logs are forwarded to rsyslog by setting ForwardToSyslog to yes in the systemd-journald configuration: #!/usr/bin/env bash { l_analyze_cmd="$(readlink -e /bin/systemd-analyze || \ readlink -e /usr/bin/systemd-analyze)" l_conf_file="systemd/journald.conf" l_block="Journal" l_option="ForwardToSyslog" l_option_value="yes" a_output=() while IFS= read -r l_file; do l_file="${l_file//# /}" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poi '^\h*'"$l_option"'\h*=\h*\H+\b' | tail -n 1)" l_option_value="$(cut -d= -f2 <<< "$l_opt" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - \"$l_option\" is set to: \"$l_option_value\"" \ " in: \"$l_file\"") done < <("$l_analyze_cmd" cat-config "$l_conf_file" | tac | \ grep -Pio '^\h*#\h*\/[^#\n\r\h]+\.conf\b') if [ "${#a_output[@]}" -le "0" ]; then l_file="/etc/$l_conf_file" l_opt="$(awk '/\['"$l_block"'\]/{a=1;next}/\[/{a=0}a' "$l_file" \ 2>/dev/null | grep -Poim 1 '^(\h*#)?\h*'"$l_option"'\h*=\h*\H+\b')" l_option_value="$(cut -d= -f2 <<< "${l_opt//# /}" | xargs)" [ -n "$l_option_value" ] && \ a_output+=(" - The default value: \"${l_opt//#/}\"" \ " is being used in the configuration") fi [ "${#a_output[@]}" -gt "0" ] && printf '%s\n' "" "${a_output[@]}" "" } Run the following command to verify systemd-journald.service and rsyslog.service are loaded and active: # systemctl list-units --type service | grep -P -- '(journald|rsyslog)' Output should be similar to: rsyslog.service loaded active running System Logging Service systemd-journald.service loaded active running Journal Service Page 703 Internal Only - General Remediation: - IF - Journald is the preferred method for capturing logs, this section and Recommendation should be skipped and the "Configure Journald" section followed. - IF - rsyslog is the preferred method for capturing logs: Set the following parameter in the [Journal] section in /etc/systemd/journald.conf or a file in /etc/systemd/journald.conf.d/ ending in .conf: ForwardToSyslog=yes Example: #!/usr/bin/env bash { [ ! -d /etc/systemd/journald.conf.d/ ] && mkdir /etc/systemd/journald.conf.d/ if grep -Psq -- '^\h*\[Journal\] /etc/systemd/journald.conf.d/60- journald.conf; then printf '%s\n' "ForwardToSyslog=yes" >> /etc/systemd/journald.conf.d/60- journald.conf else printf '%s\n' "[Journal]" "ForwardToSyslog=yes" >> /etc/systemd/journald.conf.d/60-journald.conf fi } Note: Drop-in configuration files have higher precedence and override the main configuration file. Files in the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic order, regardless of in which of the subdirectories they reside. When multiple files specify the same option, for options which accept just a single value, the entry in the file sorted last takes precedence, and for options which accept a list of values, entries are collected as they occur in the sorted files. Run to following command to update the parameters in the service: Restart systemd-journald.service: # systemctl reload-or-restart systemd-journald.service References: 1. NIST SP 800-53 Rev. 5: AC-3, AU-2, AU-4, AU-12, MP-2 2. SYSTEMD-JOURNALD.SERVICE(8) 3. JOURNALD.CONF(5) Page 704 Internal Only - General Additional Information: As noted in the systemd-journald man pages, systemd-journald logs may be exported to rsyslog either through the process mentioned here, or through a facility like systemd-journald.service. There are trade-offs involved in each implementation, where ForwardToSyslog will immediately capture all events (and forward to an external log server, if properly configured), but may not capture all boot-up activities. Mechanisms such as systemd-journald.service, on the other hand, will record bootup events, but may delay sending the information to rsyslog, leading to the potential for log manipulation prior to export. Be aware of the limitations of all tools employed to secure a system. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.9 Centralize Audit Logs v8 Centralize, to the extent possible, audit log collection and retention across ● ● enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. 6.5 Central Log Management v7 Ensure that appropriate logs are being aggregated to a central log ● ● management system for analysis and review. Page 705 Internal Only - General 6.1.2.4 Ensure rsyslog log file creation mode is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog will create logfiles that do not already exist on the system. The global() configuration object umask, available in rsyslog 8.26.0+, sets the rsyslogd process’ umask. If not specified, the system-provided default is used. The value given must always be a 4-digit octal number, with the initial digit being zero. The legacy $umask parameter sets the rsyslogd process' umask. If not specified, the system-provided default is used. The value given must always be a 4-digit octal number, with the initial digit being zero. The legacy $FileCreateMode parameter allows the setting of the mode with which rsyslogd creates new files. If not specified, the value 0644 is used. The value given must always be a 4-digit octal number, with the initial digit being zero. Please note that the actual permission depend on rsyslogd process umask. If in doubt, use $umask 0000 right at the beginning of the configuration file to remove any restrictions. The legacy $FileCreateMode may be specified multiple times. If so, it specifies the creation mode for all selector lines that follow until the next $FileCreateMode parameter. Order of lines is vitally important. Rationale: It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected. Audit: Run the following command Run the following command to verify $FileCreateMode: # grep -Ps '^\h*\$FileCreateMode\h+0[0,2,4,6][0,2,4]0\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Verify the output is includes 0640 or more restrictive: $FileCreateMode 0640 Should a site policy dictate less restrictive permissions, ensure to follow said policy. NOTE: More restrictive permissions such as 0600 is implicitly sufficient. Page 706 Internal Only - General Remediation: Edit either /etc/rsyslog.conf or a dedicated .conf file in /etc/rsyslog.d/ and set $FileCreateMode to 0640 or more restrictive: $FileCreateMode 0640 Restart the service: # systemctl restart rsyslog References: 1. RSYSLOG.CONF(5) 2. NIST SP 800-53 Rev. 5: AC-3, AC-6, MP-2 3. https://www.rsyslog.com/doc/ CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote ● ● ● file systems, databases, and applications. 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 5.1 Establish Secure Configurations v7 Maintain documented, standard security configuration standards for all ● ● ● authorized operating systems and software. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 707 Internal Only - General 6.1.2.5 Ensure rsyslog logging is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files specifies rules for logging and which files are to be used to log certain classes of messages. Rationale: A great deal of important security-related information is sent via rsyslog (e.g., successful and failed su attempts, failed login attempts, root login attempts, etc.). Audit: Review the contents of /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files to ensure appropriate logging is set. In addition, run the following command and verify that the log files are logging information as expected: # ls -l /var/log/ Remediation: Edit the following lines in the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files as appropriate for your environment. Note: The below configuration is shown for example purposes only. Due care should be given to how the organization wishes to store log data. *.emerg :omusrmsg:* auth,authpriv.* /var/log/secure mail.* -/var/log/mail mail.info -/var/log/mail.info mail.warning -/var/log/mail.warn mail.err /var/log/mail.err cron.* /var/log/cron *.=warning;*.=err -/var/log/warn *.crit /var/log/warn *.*;mail.none;news.none -/var/log/messages local0,local1.* -/var/log/localmessages local2,local3.* -/var/log/localmessages local4,local5.* -/var/log/localmessages local6,local7.* -/var/log/localmessages Run the following command to reload the rsyslogd configuration: # systemctl restart rsyslog Page 708 Internal Only - General References: 1. See the rsyslog.conf(5) man page for more information. 2. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 709 Internal Only - General 6.1.2.6 Ensure rsyslog is configured to send logs to a remote log host (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog supports the ability to send log events it gathers to a remote log host or to receive messages from remote hosts, thus enabling centralized log management. Rationale: Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system. Audit: Review the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and verify that logs are sent to a central host: basic format # grep "^*.*[^I][^I]*@" /etc/rsyslog.conf /etc/rsyslog.d/*.conf Output should include @@: Example: *.* @@loghost.example.com advanced format # grep -Psi -- '^\s*([^#]+\s+)?action\(([^#]+\s+)?\btarget=\"?[^#"]+\"?\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Output should include target=: Example: *.* action(type="omfwd" target="loghost.example.com" port="514" protocol="tcp" Page 710 Internal Only - General Remediation: Edit the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and add the following line (where loghost.example.com is the name of your central log host). The target directive may either be a fully qualified domain name or an IP address. Example: *.* action(type="omfwd" target="loghost.example.com" port="514" protocol="tcp" action.resumeRetryCount="100" queue.type="LinkedList" queue.size="1000") Run the following command to reload rsyslog.service: # systemctl reload-or-restart rsyslog.service References: 1. See the rsyslog.conf(5) man page for more information. 2. NIST SP 800-53 Rev. 5: AU-6 3. https://www.rsyslog.com/doc/ Additional Information: In addition, see the rsyslog documentation for implementation details of TLS. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 711 Internal Only - General 6.1.2.7 Ensure rsyslog is not configured to receive logs from a remote client (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: rsyslog supports the ability to receive messages from remote hosts, thus acting as a log server. Clients should not receive data from other hosts. Rationale: If a client is configured to also receive data, thus turning it into a server, the client system is acting outside its operational boundary. Audit: Review the /etc/rsyslog.conf and /etc/rsyslog.d/*.conf files and verify that the system is not configured to accept incoming logs. advanced format # grep -Psi -- '^\h*module\(load=\"?imtcp\"?\)' /etc/rsyslog.conf /etc/rsyslog.d/*.conf # grep -Psi -- '^\h*input\(type=\"?imtcp\"?\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Nothing should be returned obsolete legacy format # grep -Psi -- '^\h*\$ModLoad\h+imtcp\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf # grep -Psi -- '^\h*\$InputTCPServerRun\b' /etc/rsyslog.conf /etc/rsyslog.d/*.conf Nothing should be returned Page 712 Internal Only - General Remediation: Should there be any active log server configuration found in the auditing section, modify those files and remove the specific lines highlighted by the audit. Verify none of the following entries are present in any of /etc/rsyslog.conf or /etc/rsyslog.d/*.conf. advanced format module(load="imtcp") input(type="imtcp" port="514") deprecated legacy format $ModLoad imtcp $InputTCPServerRun Restart the service: # systemctl restart rsyslog References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-7, AU-12, CM-6 2. https://www.rsyslog.com/doc/index.html CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 4.8 Uninstall or Disable Unnecessary Services on Enterprise Assets and Software v8 Uninstall or disable unnecessary services on enterprise assets and software, ● ● such as an unused file sharing service, web application module, or service function. 9.2 Ensure Only Approved Ports, Protocols and Services v7 Are Running ● ● Ensure that only network ports, protocols, and services listening on a system with validated business needs, are running on each system. Page 713 Internal Only - General 6.1.2.8 Ensure logrotate is configured (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The system includes the capability of rotating log files regularly to avoid filling up the system with logs or making the logs unmanageably large. The file /etc/logrotate.d/syslog is the configuration file used to rotate log files created by syslog or rsyslog. Rationale: By keeping the log files smaller and more manageable, a system administrator can easily archive these files to another system and spend less time looking through inordinately large log files. Audit: Review /etc/logrotate.conf and /etc/logrotate.d/* and verify logs are rotated according to site policy. Remediation: Edit /etc/logrotate.conf and /etc/logrotate.d/* to ensure logs are rotated according to site policy. References: 1. NIST SP 800-53 Rev. 5: AU-8 Additional Information: If no maxage setting is set for logrotate a situation can occur where logrotate is interrupted and fails to delete rotated log files. It is recommended to set this to a value greater than the longest any log file should exist on your system to ensure that any such log file is removed but standard rotation settings are not overridden. Page 714 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 715 Internal Only - General 6.1.3 Configure Logfiles Page 716 Internal Only - General 6.1.3.1 Ensure access to all logfiles has been configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Log files contain information from many services on the the local system, or in the event of a centralized log server, others systems logs as well. In general log files are found in /var/log/, although application can be configured to store logs elsewhere. Should your application store logs in another, ensure to run the same test on that location. Rationale: It is important that log files have the correct permissions to ensure that sensitive data is protected and that only the appropriate users / groups have access to them. Audit: Run the following script to verify that files in /var/log/ have appropriate permissions and ownership: Page 717 Internal Only - General #!/usr/bin/env bash { a_output=(); a_output2=() f_file_test_chk() { a_out2=() maxperm="$( printf '%o' $(( 0777 & ~$perm_mask)) )" [ $(( $l_mode & $perm_mask )) -gt 0 ] && \ a_out2+=(" o Mode: \"$l_mode\" should be \"$maxperm\" or more restrictive") [[ ! "$l_user" =~ $l_auser ]] && \ a_out2+=(" o Owned by: \"$l_user\" and should be owned by \"${l_auser//|/ or }\"") [[ ! "$l_group" =~ $l_agroup ]] && \ a_out2+=(" o Group owned by: \"$l_group\" and should be group owned by \"${l_agroup//|/ or }\"") [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - File: \"$l_fname\" is:" "${a_out2[@]}") } while IFS= read -r -d $'\0' l_file; do while IFS=: read -r l_fname l_mode l_user l_group; do if grep -Pq -- '\/(apt)\h*$' <<< "$(dirname "$l_fname")"; then perm_mask='0133' l_auser="root" l_agroup="(root|adm)"; f_file_test_chk else case "$(basename "$l_fname")" in lastlog | lastlog.* | wtmp | wtmp.* | wtmp-* | btmp | btmp.* | btmp-* | README) perm_mask='0113' l_auser="root" l_agroup="(root|utmp)" f_file_test_chk ;; cloud-init.log* | localmessages* | waagent.log*) perm_mask='0133' l_auser="(root|syslog)" l_agroup="(root|adm)" file_test_chk ;; secure{,*.*,.*,-*} | auth.log | syslog | messages) perm_mask='0137' l_auser="(root|syslog)" l_agroup="(root|adm)" f_file_test_chk ;; SSSD | sssd) perm_mask='0117' l_auser="(root|SSSD)" l_agroup="(root|SSSD)" f_file_test_chk ;; gdm | gdm3) perm_mask='0117' l_auser="root" l_agroup="(root|gdm|gdm3)" f_file_test_chk ;; *.journal | *.journal~) perm_mask='0137' l_auser="root" l_agroup="(root|systemd-journal)" f_file_test_chk ;; *) perm_mask='0137' l_auser="(root|syslog)" l_agroup="(root|adm)" if [ "$l_user" = "root" ] || ! grep -Pq -- "^\h*$(awk -F: '$1=="'"$l_user"'" {print $7}' /etc/passwd)\b" /etc/shells; then ! grep -Pq -- "$l_auser" <<< "$l_user" && l_auser="(root|syslog|$l_user)" ! grep -Pq -- "$l_agroup" <<< "$l_group" && l_agroup="(root|adm|$l_group)" fi f_file_test_chk ;; esac fi done < <(stat -Lc '%n:%#a:%U:%G' "$l_file") done < <(find -L /var/log -type f \( -perm /0137 -o ! -user root -o ! -group root \) -print0) if [ "${#a_output2[@]}" -le 0 ]; then a_output+=(" - All files in \"/var/log/\" have appropriate permissions and ownership") printf '\n%s' "- Audit Result:" " ** PASS **" "${a_output[@]}" "" else printf '\n%s' "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" "" fi } Page 718 Internal Only - General Remediation: Run the following script to update permissions and ownership on files in /var/log. Although the script is not destructive, ensure that the output is captured in the event that the remediation causes issues. Page 719 Internal Only - General #!/usr/bin/env bash { a_output2=() f_file_test_fix() { a_out2=() maxperm="$( printf '%o' $(( 0777 & ~$perm_mask)) )" if [ $(( $l_mode & $perm_mask )) -gt 0 ]; then a_out2+=(" o Mode: \"$l_mode\" should be \"$maxperm\" or more restrictive" " x Removing excess permissions") chmod "$l_rperms" "$l_fname" fi if [[ ! "$l_user" =~ $l_auser ]]; then a_out2+=(" o Owned by: \"$l_user\" and should be owned by \"${l_auser//|/ or }\"" " x Changing ownership to: \"$l_fix_account\"") chown "$l_fix_account" "$l_fname" fi if [[ ! "$l_group" =~ $l_agroup ]]; then a_out2+=(" o Group owned by: \"$l_group\" and should be group owned by \"${l_agroup//|/ or }\"" " x Changing group ownership to: \"$l_fix_account\"") chgrp "$l_fix_account" "$l_fname" fi [ "${#a_out2[@]}" -gt 0 ] && a_output2+=(" - File: \"$l_fname\" is:" "${a_out2[@]}") } l_fix_account='root' while IFS= read -r -d $'\0' l_file; do while IFS=: read -r l_fname l_mode l_user l_group; do if grep -Pq -- '\/(apt)\h*$' <<< "$(dirname "$l_fname")"; then perm_mask='0133' l_rperms="u-x,go-wx" l_auser="root" l_agroup="(root|adm)"; f_file_test_fix else case "$(basename "$l_fname")" in lastlog | lastlog.* | wtmp | wtmp.* | wtmp-* | btmp | btmp.* | btmp-* | README) perm_mask='0113' l_rperms="ug-x,o-wx" l_auser="root" l_agroup="(root|utmp)" f_file_test_fix ;; cloud-init.log* | localmessages* | waagent.log*) perm_mask='0133' l_rperms="u-x,go-wx" l_auser="(root|syslog)" l_agroup="(root|adm)" file_test_fix ;; secure | auth.log | syslog | messages) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="(root|syslog)" l_agroup="(root|adm)" f_file_test_fix ;; SSSD | sssd) perm_mask='0117' l_rperms="ug-x,o-rwx" l_auser="(root|SSSD)" l_agroup="(root|SSSD)" f_file_test_fix ;; gdm | gdm3) perm_mask='0117' l_rperms="ug-x,o-rwx" l_auser="root" l_agroup="(root|gdm|gdm3)" f_file_test_fix ;; *.journal | *.journal~) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="root" l_agroup="(root|systemd- journal)" f_file_test_fix ;; *) perm_mask='0137' l_rperms="u-x,g-wx,o-rwx" l_auser="(root|syslog)" l_agroup="(root|adm)" if [ "$l_user" = "root" ] || ! grep -Pq -- "^\h*$(awk -F: '$1=="'"$l_user"'" {print $7}' /etc/passwd)\b" /etc/shells; then ! grep -Pq -- "$l_auser" <<< "$l_user" && l_auser="(root|syslog|$l_user)" ! grep -Pq -- "$l_agroup" <<< "$l_group" && l_agroup="(root|adm|$l_group)" fi f_file_test_fix ;; esac fi done < <(stat -Lc '%n:%#a:%U:%G' "$l_file") done < <(find -L /var/log -type f \( -perm /0137 -o ! -user root -o ! -group root \) -print0) if [ "${#a_output2[@]}" -le 0 ]; then # If all files passed, then we report no changes a_output+=(" - All files in \"/var/log/\" have appropriate permissions and ownership") printf '\n%s' "- All files in \"/var/log/\" have appropriate permissions and ownership" " o No changes required" "" else printf '\n%s' "${a_output2[@]}" "" fi } Page 720 Internal Only - General Note: You may also need to change the configuration for your logging software or services for any logs that had incorrect permissions. If there are services that log to other locations, ensure that those log files have the appropriate access configured. References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 721 Internal Only - General 6.2 System Auditing The Linux Auditing System operates on a set of rules that collects certain types of system activity to facilitate incident investigation, detect unauthorized access or modification of data. By default events will be logged to /var/log/audit/audit.log, which can be configured in /etc/audit/auditd.conf. The following types of audit rules can be specified: • Control rules: Configuration of the auditing system. • File system rules: Allow the auditing of access to a particular file or a directory. Also known as file watches. • System call rules: Allow logging of system calls that any specified program makes. Audit rules can be set: • On the command line using the auditctl utility. These rules are not persistent across reboots. • In /etc/audit/audit.rules. These rules have to be merged and loaded before they are active. Notes: • For 64 bit systems that have arch as a rule parameter, you will need two rules: one for 64 bit and one for 32 bit systems calls. • If the auditing system is configured to be locked (-e 2), a system reboot will be required in order to load any changes. • Key names are optional on the rules and will not be used as a compliance auditing. The usage of key names is highly recommended as it facilitates organization and searching, as such, all remediation steps will have key names supplied. • It is best practice to store the rules, in number prepended files, in /etc/audit/rules.d/. Rules must end in a .rules suffix. This then requires the use of augenrules to merge all the rules into /etc/audit/audit.rules based on their their alphabetical (lexical) sort order. All benchmark recommendations follow this best practice for remediation, specifically using the prefix of 50 which is centre weighed if all rule sets make use of the number prepending naming convention. • Your system may have been customized to change the default UID_MIN. All samples output uses 1000, but this value will not be used in compliance auditing. To confirm the UID_MIN for your system, run the following command: awk '/^\s*UID_MIN/{print $2}' /etc/login.defs Normalization Page 722 Internal Only - General The Audit system normalizes some entries, so when you look at the sample output keep in mind that: • With regards to users whose login UID is not set, the values -1 / unset / 4294967295 are equivalent and normalized to -1. • When comparing field types and both sides of the comparison is valid fields types, such aseuid!=uid, then the auditing system may normalize such that the output is uid!=euid. • Some parts of the rule may be rearranged whilst others are dependant on previous syntax. For example, the following two statements are the same: -a always,exit -F arch=b64 -S execve -C uid!=euid -F auid!=-1 -F key=user_emulation and -a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation Capacity planning The recommendations in this section implement auditing policies that not only produces large quantities of logged data, but may also negatively impact system performance. Capacity planning is critical in order not to adversely impact production environments. • Disk space. If a significantly large set of events are captured, additional on system or off system storage may need to be allocated. If the logs are not sent to a remote log server, ensure that log rotation is implemented else the disk will fill up and the system will halt. Even when logs are sent to a log server, ensure sufficient disk space to allow caching of logs in the case of temporary network outages. • Disk IO. It is not just the amount of data collected that should be considered, but the rate at which logs are generated. • CPU overhead. System call rules might incur considerable CPU overhead. Test the systems open/close syscalls per second with and without the rules to gauge the impact of the rules. Page 723 Internal Only - General 6.2.1 Configure auditd Service The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Page 724 Internal Only - General 6.2.1.1 Ensure auditd packages are installed (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: auditd is the userspace component to the Linux Auditing System. It's responsible for writing audit records to the disk Rationale: The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Audit: Run the following command and verify auditd is installed: # dpkg-query -s auditd &>/dev/null && echo auditd is installed auditd is installed Run the following command to verify audispd-plugins is installed: # dpkg-query -s audispd-plugins &>/dev/null && echo audispd-plugins is installed audispd-plugins is installed Remediation: Run the following command to Install auditd and audispd-plugins # apt install auditd audispd-plugins References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12, SI-5 2. STIG ID: UBTU-20-010182 | RULE ID: SV-238298r958506 | CAT II 3. STIG ID: UBTU-22-653015 | RULE ID: SV-260591r1015023 | CAT II Page 725 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 726 Internal Only - General 6.2.1.2 Ensure auditd service is enabled and active (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Turn on the auditd daemon to record system events. Rationale: The capturing of system events provides system administrators with information to allow them to determine if unauthorized access to their system is occurring. Audit: Run the following command to verify auditd is enabled: # systemctl is-enabled auditd | grep '^enabled' enabled Verify result is "enabled". Run the following command to verify auditd is active: # systemctl is-active auditd | grep '^active' active Verify result is active Remediation: Run the following commands to unmask, enable and start auditd: # systemctl unmask auditd # systemctl enable auditd # systemctl start auditd References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 2. STIG ID: UBTU-20-010182 | RULE ID: SV-238298r958506 | CAT II 3. STIG ID: UBTU-22-653015 | RULE ID: SV-260591r1015023 | CAT II Page 727 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 728 Internal Only - General 6.2.1.3 Ensure auditing for processes that start prior to auditd is enabled (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Configure grub2 so that processes that are capable of being audited can be audited even if they start up prior to auditd startup. Rationale: Audit events need to be captured on processes that start up prior to auditd , so that potential malicious activity cannot go undetected. Audit: Run the following command: # find /boot -type f -name 'grub.cfg' -exec grep -Ph -- '^\h*linux' {} + | grep -v 'audit=1' Nothing should be returned. Remediation: Edit /etc/default/grub and add audit=1 to GRUB_CMDLINE_LINUX: Example: GRUB_CMDLINE_LINUX="audit=1" Run the following command to update the grub2 configuration: # update-grub References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 2. STIG ID: UBTU-20-010198 | RULE ID: SV-238299r991555 | CAT II 3. STIG ID: UBTU-22-212015 | RULE ID: SV-260471r991555 | CAT II Additional Information: This recommendation is designed around the grub2 bootloader, if another bootloader is in use in your environment enact equivalent settings. Page 729 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 730 Internal Only - General 6.2.1.4 Ensure audit_backlog_limit is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: In the kernel-level audit subsystem, a socket buffer queue is used to hold audit events. Whenever a new audit event is received, it is logged and prepared to be added to this queue. The kernel boot parameter audit_backlog_limit=N, with N representing the amount of messages, will ensure that a queue cannot grow beyond a certain size. If an audit event is logged which would grow the queue beyond this limit, then a failure occurs and is handled according to the system configuration Rationale: If an audit event is logged which would grow the queue beyond the audit_backlog_limit, then a failure occurs, auditd records will be lost, and potential malicious activity could go undetected. Audit: Run the following command and verify the audit_backlog_limit= parameter is set: # find /boot -type f -name 'grub.cfg' -exec grep -Ph -- '^\h*linux' {} + | grep -Pv 'audit_backlog_limit=\d+\b' Nothing should be returned. Remediation: Edit /etc/default/grub and add audit_backlog_limit=N to GRUB_CMDLINE_LINUX. The recommended size for N is 8192 or larger. Example: GRUB_CMDLINE_LINUX="audit_backlog_limit=8192" Run the following command to update the grub2 configuration: # update-grub Default Value: if audit_backlog_limit is not set, the system defaults to audit_backlog_limit=64 References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-3, AU-12 Page 731 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and ● ● other useful elements. Page 732 Internal Only - General 6.2.2 Configure Data Retention When auditing, it is important to carefully configure the storage requirements for audit logs. By default, auditd will max out the log files at 5MB and retain only 4 copies of them. Older versions will be deleted. It is possible on a system that the 20 MBs of audit logs may fill up the system causing loss of audit data. While the recommendations here provide guidance, check your site policy for audit storage requirements. Page 733 Internal Only - General 6.2.2.1 Ensure audit log storage size is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Configure the maximum size of the audit log file. Once the log reaches the maximum size, it will be rotated and a new log file will be started. Rationale: It is important that an appropriate size is determined for log files so that they do not impact the system and audit data is not lost. Audit: Run the following command and ensure output is in compliance with site policy: # grep -Po -- '^\h*max_log_file\h*=\h*\d+\b' /etc/audit/auditd.conf max_log_file = Remediation: Set the following parameter in /etc/audit/auditd.conf in accordance with site policy: max_log_file = Default Value: max_log_file = 8 References: 1. NIST SP 800-53 Rev. 5: AU-8 Additional Information: The max_log_file parameter is measured in megabytes. Other methods of log rotation may be appropriate based on site policy. One example is time-based rotation strategies which don't have native support in auditd configurations. Manual audit of custom configurations should be evaluated for effectiveness and completeness. Page 734 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 735 Internal Only - General 6.2.2.2 Ensure audit logs are not automatically deleted (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The max_log_file_action setting determines how to handle the audit log file reaching the max file size. A value of keep_logs will rotate the logs but never delete old logs. Rationale: In high security contexts, the benefits of maintaining a long audit history exceed the cost of storing the audit history. Audit: Run the following command and verify output matches: # grep max_log_file_action /etc/audit/auditd.conf max_log_file_action = keep_logs Remediation: Set the following parameter in /etc/audit/auditd.conf: max_log_file_action = keep_logs References: 1. NIST SP 800-53 Rev. 5: AU-8 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.4 Ensure adequate storage for logs v7 Ensure that all systems that store logs have adequate storage space for the ● ● logs generated. Page 736 Internal Only - General 6.2.2.3 Ensure system is disabled when audit logs are full (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditd daemon can be configured to halt the system or put the system in single user mode, if no free space is available or an error is detected on the partition that holds the audit log files. The disk_full_action parameter tells the system what action to take when no free space is available on the partition that holds the audit log files. Valid values are ignore, syslog, rotate, exec, suspend, single, and halt. • ignore, the audit daemon will issue a syslog message but no other action is taken • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system The disk_error_action parameter tells the system what action to take when an error is detected on the partition that holds the audit log files. Valid values are ignore, syslog, exec, suspend, single, and halt. • ignore, the audit daemon will not take any action • syslog, the audit daemon will issue no more than 5 consecutive warnings to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system Rationale: In high security contexts, the risk of detecting unauthorized access or nonrepudiation exceeds the benefit of the system's availability. Page 737 Internal Only - General Impact: disk_full_action parameter: • Set to halt - the auditd daemon will shutdown the system when the disk partition containing the audit logs becomes full. • Set to single - the auditd daemon will put the computer system in single user mode when the disk partition containing the audit logs becomes full. disk_error_action parameter: • Set to halt - the auditd daemon will shutdown the system when an error is detected on the partition that holds the audit log files. • Set to single - the auditd daemon will put the computer system in single user mode when an error is detected on the partition that holds the audit log files. • Set to syslog - the auditd daemon will issue no more than 5 consecutive warnings to syslog when an error is detected on the partition that holds the audit log files. Audit: Run the following command and verify the disk_full_action is set to either halt or single: # grep -Pi -- '^\h*disk_full_action\h*=\h*(halt|single)\b' /etc/audit/auditd.conf disk_full_action = Run the following command and verify the disk_error_action is set to syslog, single, or halt: # grep -Pi -- '^\h*disk_error_action\h*=\h*(syslog|single|halt)\b' /etc/audit/auditd.conf disk_error_action = Remediation: Set one of the following parameters in /etc/audit/auditd.conf depending on your local security policies. disk_full_action = disk_error_action = Example: disk_full_action = halt disk_error_action = halt Page 738 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-8, AU-12, SI-5 2. AUDITD.CONF(5) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. Page 739 Internal Only - General 6.2.2.4 Ensure system warns when audit logs are low on space (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The auditd daemon can be configured to halt the system, put the system in single user mode or send a warning message, if the partition that holds the audit log files is low on space. The space_left_action parameter tells the system what action to take when the system has detected that it is starting to get low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt. • ignore, the audit daemon does nothing • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • email, the audit daemon will send a warning to the email account specified in action_mail_acct as well as sending the message to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system The admin_space_left_action parameter tells the system what action to take when the system has detected that it is low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt. • ignore, the audit daemon does nothing • syslog, the audit daemon will issue a warning to syslog • rotate, the audit daemon will rotate logs, losing the oldest to free up space • email, the audit daemon will send a warning to the email account specified in action_mail_acct as well as sending the message to syslog • exec, /path-to-script will execute the script. You cannot pass parameters to the script. The script is also responsible for telling the auditd daemon to resume logging once its completed its action • suspend, the audit daemon will stop writing records to the disk • single, the audit daemon will put the computer system in single user mode • halt, the audit daemon will shut down the system Page 740 Internal Only - General Rationale: In high security contexts, the risk of detecting unauthorized access or nonrepudiation exceeds the benefit of the system's availability. Impact: If the admin_space_left_action is set to single the audit daemon will put the computer system in single user mode. Audit: Run the following command and verify the space_left_action is set to email, exec, single, or halt: grep -Pi -- '^\h*space_left_action\h*=\h*(email|exec|single|halt)\b' /etc/audit/auditd.conf Verify the output is email, exec, single, or halt Example output space_left_action = email Run the following command and verify the admin_space_left_action is set to single - OR - halt: grep -Pi -- '^\h*admin_space_left_action\h*=\h*(single|halt)\b' /etc/audit/auditd.conf Verify the output is single or halt Example output: admin_space_left_action = single Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email Remediation: Set the space_left_action parameter in /etc/audit/auditd.conf to email, exec, single, or halt: Example: space_left_action = email Set the admin_space_left_action parameter in /etc/audit/auditd.conf to single or halt: Example: admin_space_left_action = single Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email Page 741 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-8, AU-12, SI-5 2. AUDITD.CONF(5) CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 8.3 Ensure Adequate Audit Log Storage v8 Ensure that logging destinations maintain adequate storage to comply with ● ● ● the enterprise’s audit log management process. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 742 Internal Only - General 6.2.3 Configure auditd Rules The Audit system operates on a set of rules that define what is to be captured in the log files. The following types of Audit rules can be specified: • Control rules: Allow the Audit system's behavior and some of its configuration to be modified. • File system rules: Allow the auditing of access to a particular file or a directory. (Also known as file watches) • System call rules: Allow logging of system calls that any specified program makes. Audit rules can be set: • on the command line using the auditctl utility. Note that these rules are not persistent across reboots. • in a file ending in .rules in the /etc/audit/rules.d/ directory. Note: The Linux Benchmarks are written and tested against x86_64 processor architecture. If you are running a different processor type, please review and update the audit rules for the processor architecture of the system Page 743 Internal Only - General 6.2.3.1 Ensure changes to system administration scope (sudoers) is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor scope changes for system administrators. If the system has been properly configured to force system administrators to log in as themselves first and then use the sudo command to execute privileged commands, it is possible to monitor changes in scope. The file /etc/sudoers, or files in /etc/sudoers.d, will be written to when the file(s) or related attributes have changed. The audit records will be tagged with the identifier "scope". Rationale: Changes in the /etc/sudoers and /etc/sudoers.d files can indicate that an unauthorized change has been made to the scope of system administrator activity. Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-w/ \ &&/\/etc\/sudoers/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -w /etc/sudoers -p wa -k scope -w /etc/sudoers.d -p wa -k scope Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-w/ \ &&/\/etc\/sudoers/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -w /etc/sudoers -p wa -k scope -w /etc/sudoers.d -p wa -k scope Page 744 Internal Only - General Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor scope changes for system administrators. Example: # printf " -w /etc/sudoers -p wa -k scope -w /etc/sudoers.d -p wa -k scope " >> /etc/audit/rules.d/50-scope.rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 745 Internal Only - General 6.2.3.2 Ensure actions as another user are always logged (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: sudo provides users with temporary elevated privileges to perform operations, either as the superuser or another user. Rationale: Creating an audit log of users with temporary elevated privileges and the operation(s) they performed is essential to reporting. Administrators will want to correlate the events written to the audit trail with the records written to sudo's logfile to verify if unauthorized commands have been executed. Page 746 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&(/ -C *euid!=uid/||/ -C *uid!=euid/) \ &&/ -S *execve/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation -a always,exit -F arch=b32 -C euid!=uid -F auid!=unset -S execve -k user_emulation Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&(/ -C *euid!=uid/||/ -C *uid!=euid/) \ &&/ -S *execve/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -a always,exit -F arch=b64 -S execve -C uid!=euid -F auid!=-1 -F key=user_emulation -a always,exit -F arch=b32 -S execve -C uid!=euid -F auid!=-1 -F key=user_emulation Page 747 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor elevated privileges. Example: # printf " -a always,exit -F arch=b64 -C euid!=uid -F auid!=unset -S execve -k user_emulation -a always,exit -F arch=b32 -C euid!=uid -F auid!=unset -S execve -k user_emulation " >> /etc/audit/rules.d/50-user_emulation.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 748 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. Page 749 Internal Only - General 6.2.3.3 Ensure events that modify the sudo log file are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the sudo log file. If the system has been properly configured to disable the use of the su command and force all administrators to have to log in first and then use sudo to execute privileged commands, then all administrator commands will be logged to /var/log/sudo.log . Any time a command is executed, an audit event will be triggered as the /var/log/sudo.log file will be opened for write and the executed administration command will be written to the log. Rationale: Changes in /var/log/sudo.log indicate that an administrator has executed a command or the log file itself has been tampered with. Administrators will want to correlate the events written to the audit trail with the records written to /var/log/sudo.log to verify if unauthorized commands have been executed. Page 750 Internal Only - General Audit: Note: This recommendation requires that the sudo logfile is configured. See guidance provided in the recommendation "Ensure sudo log file exists" On disk configuration Run the following command to check the on disk rules: # { SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g' -e 's|/|\\/|g') [ -n "${SUDO_LOG_FILE}" ] && awk "/^ *-w/ \ &&/"${SUDO_LOG_FILE}"/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n" } Verify output of matches: -w /var/log/sudo.log -p wa -k sudo_log_file Running configuration Run the following command to check loaded rules: # { SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g' -e 's|/|\\/|g') [ -n "${SUDO_LOG_FILE}" ] && auditctl -l | awk "/^ *-w/ \ &&/"${SUDO_LOG_FILE}"/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n" } Verify output matches: -w /var/log/sudo.log -p wa -k sudo_log_file Page 751 Internal Only - General Remediation: Note: This recommendation requires that the sudo logfile is configured. See guidance provided in the recommendation "Ensure sudo log file exists" Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the sudo log file. Example: # { SUDO_LOG_FILE=$(grep -r logfile /etc/sudoers* | sed -e 's/.*logfile=//;s/,? .*//' -e 's/"//g') [ -n "${SUDO_LOG_FILE}" ] && printf " -w ${SUDO_LOG_FILE} -p wa -k sudo_log_file " >> /etc/audit/rules.d/50-sudo.rules || printf "ERROR: Variable 'SUDO_LOG_FILE' is unset.\n" } Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. Page 752 Internal Only - General 6.2.3.4 Ensure events that modify date and time information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Capture events where the system date and/or time has been modified. The parameters in this section are set to determine if the; • adjtimex - tune kernel clock • settimeofday - set time using timeval and timezone structures • stime - using seconds since 1/1/1970 • clock_settime - allows for the setting of several internal clocks and timers system calls have been executed. Further, ensure to write an audit record to the configured audit log file upon exit, tagging the records with a unique identifier such as "time-change". Rationale: Unexpected changes in system date and/or time could be a sign of malicious activity on the system. Page 753 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&/ -S/ \ &&(/adjtimex/ \ ||/settimeofday/ \ ||/clock_settime/ ) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules awk '/^ *-w/ \ &&/\/etc\/localtime/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules } Verify output of matches: -a always,exit -F arch=b64 -S adjtimex,settimeofday -k time-change -a always,exit -F arch=b32 -S adjtimex,settimeofday -k time-change -a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -k time-change -a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -k time-change -w /etc/localtime -p wa -k time-change Running configuration Run the following command to check loaded rules: # { auditctl -l | awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&/ -S/ \ &&(/adjtimex/ \ ||/settimeofday/ \ ||/clock_settime/ ) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' auditctl -l | awk '/^ *-w/ \ &&/\/etc\/localtime/ \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' } Verify the output includes: -a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=time-change -a always,exit -F arch=b32 -S settimeofday,adjtimex -F key=time-change -a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -F key=time-change -a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -F key=time-change -w /etc/localtime -p wa -k time-change Page 754 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify date and time information. Example: # printf " -a always,exit -F arch=b64 -S adjtimex,settimeofday -k time-change -a always,exit -F arch=b32 -S adjtimex,settimeofday -k time-change -a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -k time-change -a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -k time-change -w /etc/localtime -p wa -k time-change " >> /etc/audit/rules.d/50-time-change.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 755 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 756 Internal Only - General 6.2.3.5 Ensure events that modify the system's network environment are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record changes to network environment files or system calls. The below parameters monitors the following system calls, and write an audit event on system call exit: • sethostname - set the systems host name • setdomainname - set the systems domain name The files being monitored are: • /etc/issue and /etc/issue.net - messages displayed pre-login • /etc/hosts - file containing host names and associated IP addresses • /etc/networks - symbolic names for networks • /etc/network/ - directory containing network interface scripts and configurations files • /etc/netplan/ - central location for YAML networking configurations files Rationale: Monitoring system events that change network environments, such as sethostname and setdomainname, helps identify unauthorized alterations to host and domain names, which could compromise security settings reliant on these names. Changes to /etc/hosts can signal unauthorized attempts to alter machine associations with IP addresses, potentially redirecting users and processes to unintended destinations. Surveillance of /etc/issue and /etc/issue.net is crucial to detect intruders inserting false information to deceive users. Monitoring /etc/network/ reveals modifications to network interfaces or scripts that may jeopardize system availability or security. Additionally, tracking changes in the /etc/netplan/ directory ensures swift detection of unauthorized adjustments to network configurations. All audit records should be appropriately tagged for relevance Audit: On disk configuration Run the following commands to check the on disk rules: Page 757 Internal Only - General # awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&/ -S/ \ &&(/sethostname/ \ ||/setdomainname/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules # awk '/^ *-w/ \ &&(/\/etc\/issue/ \ ||/\/etc\/issue.net/ \ ||/\/etc\/hosts/ \ ||/\/etc\/network \ ||/\/etc\/netplan) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale -a always,exit -F arch=b32 -S sethostname,setdomainname -k system-locale -w /etc/issue -p wa -k system-locale -w /etc/issue.net -p wa -k system-locale -w /etc/hosts -p wa -k system-locale -w /etc/networks -p wa -k system-locale -w /etc/network -p wa -k system-locale -w /etc/netplan -p wa -k system-locale Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&/ -S/ \ &&(/sethostname/ \ ||/setdomainname/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' # auditctl -l | awk '/^ *-w/ \ &&(/\/etc\/issue/ \ ||/\/etc\/issue.net/ \ ||/\/etc\/hosts/ \ ||/\/etc\/network \ ||/\/etc\/netplan) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output includes: -a always,exit -F arch=b64 -S sethostname,setdomainname -F key=system-locale -a always,exit -F arch=b32 -S sethostname,setdomainname -F key=system-locale -w /etc/issue -p wa -k system-locale -w /etc/issue.net -p wa -k system-locale -w /etc/hosts -p wa -k system-locale -w /etc/networks -p wa -k system-locale -w /etc/network -p wa -k system-locale -w /etc/netplan -p wa -k system-locale Page 758 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's network environment. Example: # printf " -a always,exit -F arch=b64 -S sethostname,setdomainname -k system-locale -a always,exit -F arch=b32 -S sethostname,setdomainname -k system-locale -w /etc/issue -p wa -k system-locale -w /etc/issue.net -p wa -k system-locale -w /etc/hosts -p wa -k system-locale -w /etc/networks -p wa -k system-locale -w /etc/network -p wa -k system-locale -w /etc/netplan -p wa -k system-locale " >> /etc/audit/rules.d/50-system_locale.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 2. https://netplan.io/faq Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 759 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 760 Internal Only - General 6.2.3.6 Ensure use of privileged commands are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor privileged programs, those that have the setuid and/or setgid bit set on execution, to determine if unprivileged users are running these commands. Rationale: Execution of privileged commands by non-privileged users could be an indication of someone trying to gain unauthorized access to the system. Impact: Both the audit and remediation section of this recommendation will traverse all mounted file systems that is not mounted with either noexec or nosuid mount options. If there are large file systems without these mount options, such traversal will be significantly detrimental to the performance of the system. Before running either the audit or remediation section, inspect the output of the following command to determine exactly which file systems will be traversed: # findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" To exclude a particular file system due to adverse performance impacts, update the audit and remediation sections by adding a sufficiently unique string to the grep statement. The above command can be used to test the modified exclusions. Page 761 Internal Only - General Audit: On disk configuration Run the following script to check on disk rules: #!/usr/bin/env bash { for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do for PRIVILEGED in $(find "${PARTITION}" -xdev -perm /6000 -type f); do grep -qr "${PRIVILEGED}" /etc/audit/rules.d && printf "OK: '${PRIVILEGED}' found in auditing rules.\n" || printf "Warning: '${PRIVILEGED}' not found in on disk configuration.\n" done done } Verify that all output is OK. Running configuration Run the following script to check loaded rules: #!/usr/bin/env bash { RUNNING=$(auditctl -l) [ -n "${RUNNING}" ] && for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do for PRIVILEGED in $(find "${PARTITION}" -xdev -perm /6000 -type f); do printf -- "${RUNNING}" | grep -q "${PRIVILEGED}" && printf "OK: '${PRIVILEGED}' found in auditing rules.\n" || printf "Warning: '${PRIVILEGED}' not found in running configuration.\n" done done \ || printf "ERROR: Variable 'RUNNING' is unset.\n" } Verify that all output is OK. Special mount points If there are any special mount points that are not visible by default from findmnt as per the above audit, said file systems would have to be manually audited. Page 762 Internal Only - General Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor the use of privileged commands. Example script: #!/usr/bin/env bash { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) AUDIT_RULE_FILE="/etc/audit/rules.d/50-privileged.rules" NEW_DATA=() for PARTITION in $(findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,) | grep -Pv "noexec|nosuid" | awk '{print $1}'); do readarray -t DATA < <(find "${PARTITION}" -xdev -perm /6000 -type f | awk -v UID_MIN=${UID_MIN} '{print "-a always,exit -F path=" $1 " -F perm=x -F auid>="UID_MIN" -F auid!=unset -k privileged" }') for ENTRY in "${DATA[@]}"; do NEW_DATA+=("${ENTRY}") done done readarray &> /dev/null -t OLD_DATA < "${AUDIT_RULE_FILE}" COMBINED_DATA=( "${OLD_DATA[@]}" "${NEW_DATA[@]}" ) printf '%s\n' "${COMBINED_DATA[@]}" | sort -u > "${AUDIT_RULE_FILE}" } Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Special mount points If there are any special mount points that are not visible by default from just scanning /, change the PARTITION variable to the appropriate partition and re-run the remediation. References: 1. NIST SP 800-53 Rev. 5: AU-3, AU-3(1) Page 763 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 764 Internal Only - General 6.2.3.7 Ensure unsuccessful file access attempts are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor for unsuccessful attempts to access files. The following parameters are associated with system calls that control files: • creation - creat • opening - open , openat • truncation - truncate , ftruncate An audit log record will only be written if all of the following criteria is met for the user when trying to access a file: • a non-privileged user (auid>=UID_MIN) • is not a Daemon event (auid=4294967295/unset/-1) • if the system call returned EACCES (permission denied) or EPERM (some other permanent error associated with the specific system call) Rationale: Failed attempts to open, create or truncate files could be an indication that an individual or process is trying to gain unauthorized access to the system. Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&(/ -F *exit=-EACCES/||/ -F *exit=-EPERM/) \ &&/ -S/ \ &&/creat/ \ &&/open/ \ &&/truncate/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output includes: Page 765 Internal Only - General -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EACCES -F auid>=1000 -F auid!=unset -k access -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EPERM -F auid>=1000 -F auid!=unset -k access -a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=- EACCES -F auid>=1000 -F auid!=unset -k access -a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=- EPERM -F auid>=1000 -F auid!=unset -k access Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&(/ -F *exit=-EACCES/||/ -F *exit=-EPERM/) \ &&/ -S/ \ &&/creat/ \ &&/open/ \ &&/truncate/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output includes: -a always,exit -F arch=b64 -S open,truncate,ftruncate,creat,openat -F exit=- EACCES -F auid>=1000 -F auid!=-1 -F key=access -a always,exit -F arch=b64 -S open,truncate,ftruncate,creat,openat -F exit=- EPERM -F auid>=1000 -F auid!=-1 -F key=access -a always,exit -F arch=b32 -S open,truncate,ftruncate,creat,openat -F exit=- EACCES -F auid>=1000 -F auid!=-1 -F key=access -a always,exit -F arch=b32 -S open,truncate,ftruncate,creat,openat -F exit=- EPERM -F auid>=1000 -F auid!=-1 -F key=access Page 766 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor unsuccessful file access attempts. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EACCES -F auid>=${UID_MIN} -F auid!=unset -k access -a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=- EPERM -F auid>=${UID_MIN} -F auid!=unset -k access -a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=- EACCES -F auid>=${UID_MIN} -F auid!=unset -k access -a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=- EPERM -F auid>=${UID_MIN} -F auid!=unset -k access " >> /etc/audit/rules.d/50-access.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 767 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 768 Internal Only - General 6.2.3.8 Ensure events that modify user/group information are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Record events affecting the modification of user or group information, including that of passwords and old passwords if in use. • /etc/group - system groups • /etc/passwd - system users • /etc/gshadow - encrypted password for each group • /etc/shadow - system user passwords • /etc/security/opasswd - storage of old passwords if the relevant PAM module is in use • /etc/nsswitch.conf - file configures how the system uses various databases and name resolution mechanisms • /etc/pam.conf - file determines the authentication services to be used, and the order in which the services are used. • /etc/pam.d - directory contains the PAM configuration files for each PAM-aware application. The parameters in this section will watch the files to see if they have been opened for write or have had attribute changes (e.g. permissions) and tag them with the identifier "identity" in the audit log file. Rationale: Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts. Page 769 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-w/ \ &&(/\/etc\/group/ \ ||/\/etc\/passwd/ \ ||/\/etc\/gshadow/ \ ||/\/etc\/shadow/ \ ||/\/etc\/security\/opasswd/ \ ||/\/etc\/nsswitch.conf/ \ ||/\/etc\/pam.conf/ \ ||/\/etc\/pam.d/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -w /etc/group -p wa -k identity -w /etc/passwd -p wa -k identity -w /etc/gshadow -p wa -k identity -w /etc/shadow -p wa -k identity -w /etc/security/opasswd -p wa -k identity -w /etc/nsswitch.conf -p wa -k identity -w /etc/pam.conf -p wa -k identity -w /etc/pam.d -p wa -k identity Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-w/ \ &&(/\/etc\/group/ \ ||/\/etc\/passwd/ \ ||/\/etc\/gshadow/ \ ||/\/etc\/shadow/ \ ||/\/etc\/security\/opasswd/ \ ||/\/etc\/nsswitch.conf/ \ ||/\/etc\/pam.conf/ \ ||/\/etc\/pam.d/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -w /etc/group -p wa -k identity -w /etc/passwd -p wa -k identity -w /etc/gshadow -p wa -k identity -w /etc/shadow -p wa -k identity -w /etc/security/opasswd -p wa -k identity -w /etc/nsswitch.conf -p wa -k identity -w /etc/pam.conf -p wa -k identity -w /etc/pam.d -p wa -k identity Page 770 Internal Only - General Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify user/group information. Example: # printf " -w /etc/group -p wa -k identity -w /etc/passwd -p wa -k identity -w /etc/gshadow -p wa -k identity -w /etc/shadow -p wa -k identity -w /etc/security/opasswd -p wa -k identity -w /etc/nsswitch.conf -p wa -k identity -w /etc/pam.conf -p wa -k identity -w /etc/pam.d -p wa -k identity " >> /etc/audit/rules.d/50-identity.rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 2. https://manpages.debian.org/bookworm/manpages/nsswitch.conf.5.en.html 3. https://access.redhat.com/documentation/en- us/red_hat_enterprise_linux/6/html/managing_smart_cards/pam_configuration_fil es Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 771 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.8 Log and Alert on Changes to Administrative Group v7 Membership ● ● Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges. Page 772 Internal Only - General 6.2.3.9 Ensure discretionary access control permission modification events are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor changes to file permissions, attributes, ownership and group. The parameters in this section track changes for system calls that affect file permissions and attributes. The following commands and system calls effect the permissions, ownership and various attributes of files. • chmod • fchmod • fchmodat • chown • fchown • fchownat • lchown • setxattr • lsetxattr • fsetxattr • removexattr • lremovexattr • fremovexattr In all cases, an audit record will only be written for non-system user ids and will ignore Daemon events. All audit records will be tagged with the identifier "perm_mod." Rationale: Monitoring for changes in file attributes could alert a system administrator to activity that could indicate intruder activity or policy violation. Audit: Note: Output showing all audited syscalls, e.g. (-a always,exit -F arch=b64 -S chmod,fchmod,fchmodat,chmod,fchmod,fchmodat,setxattr,lsetxattr,fsetxattr,removexattr ,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod) is also acceptable. These have been separated by function on the displayed output for clarity. On disk configuration Run the following command to check the on disk rules: Page 773 Internal Only - General # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -S/ \ &&/ -F *auid>=${UID_MIN}/ \ &&(/chmod/||/fchmod/||/fchmodat/ \ ||/chown/||/fchown/||/fchownat/||/lchown/ \ ||/setxattr/||/lsetxattr/||/fsetxattr/ \ ||/removexattr/||/lremovexattr/||/fremovexattr/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod -a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F auid>=1000 -F auid!=unset -F key=perm_mod -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=unset -F key=perm_mod Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -S/ \ &&/ -F *auid>=${UID_MIN}/ \ &&(/chmod/||/fchmod/||/fchmodat/ \ ||/chown/||/fchown/||/fchownat/||/lchown/ \ ||/setxattr/||/lsetxattr/||/fsetxattr/ \ ||/removexattr/||/lremovexattr/||/fremovexattr/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: Page 774 Internal Only - General -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -F key=perm_mod -a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=1000 -F auid!=-1 -F key=perm_mod -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=1000 -F auid!=-1 -F key=perm_mod -a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F auid>=1000 -F auid!=-1 -F key=perm_mod -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=-1 -F key=perm_mod -a always,exit -F arch=b32 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=1000 -F auid!=-1 -F key=perm_mod Page 775 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor discretionary access control permission modification events. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F arch=b64 -S chmod,fchmod,fchmodat -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod -a always,exit -F arch=b64 -S chown,fchown,lchown,fchownat -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S chmod,fchmod,fchmodat -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S lchown,fchown,chown,fchownat -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod -a always,exit -F arch=b64 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod -a always,exit -F arch=b32 -S setxattr,lsetxattr,fsetxattr,removexattr,lremovexattr,fremovexattr -F auid>=${UID_MIN} -F auid!=unset -F key=perm_mod " >> /etc/audit/rules.d/50-perm_mod.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Page 776 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 777 Internal Only - General 6.2.3.10 Ensure successful file system mounts are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the use of the mount system call. The mount (and umount ) system call controls the mounting and unmounting of file systems. The parameters below configure the system to create an audit record when the mount system call is used by a non- privileged user Rationale: It is highly unusual for a non privileged user to mount file systems to the system. While tracking mount commands gives the system administrator evidence that external media may have been mounted (based on a review of the source of the mount and confirming it's an external media type), it does not conclusively indicate that data was exported to the media. System administrators who wish to determine if data were exported, would also have to track successful open, creat and truncate system calls requiring write access to a file under the mount point of the external media file system. This could give a fair indication that a write occurred. The only way to truly prove it, would be to track successful writes to the external media. Tracking write system calls could quickly fill up the audit log and is not recommended. Recommendations on configuration options to track data export to media is beyond the scope of this document. Page 778 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -S/ \ &&/mount/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=unset -k mounts -a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=unset -k mounts Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -S/ \ &&/mount/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=-1 -F key=mounts -a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=-1 -F key=mounts Page 779 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful file system mounts. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F arch=b32 -S mount -F auid>=$UID_MIN -F auid!=unset -k mounts -a always,exit -F arch=b64 -S mount -F auid>=$UID_MIN -F auid!=unset -k mounts " >> /etc/audit/rules.d/50-mounts.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: CM-6 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 780 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 781 Internal Only - General 6.2.3.11 Ensure session initiation information is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor session initiation events. The parameters in this section track changes to the files associated with session events. • /var/run/utmp - tracks all currently logged in users. • /var/log/wtmp - file tracks logins, logouts, shutdown, and reboot events. • /var/log/btmp - keeps track of failed login attempts and can be read by entering the command /usr/bin/last -f /var/log/btmp. All audit records will be tagged with the identifier "session." Rationale: Monitoring these files for changes could alert a system administrator to logins occurring at unusual hours, which could indicate intruder activity (i.e. a user logging in at a time when they do not normally log in). Page 782 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-w/ \ &&(/\/var\/run\/utmp/ \ ||/\/var\/log\/wtmp/ \ ||/\/var\/log\/btmp/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -w /var/run/utmp -p wa -k session -w /var/log/wtmp -p wa -k session -w /var/log/btmp -p wa -k session Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-w/ \ &&(/\/var\/run\/utmp/ \ ||/\/var\/log\/wtmp/ \ ||/\/var\/log\/btmp/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -w /var/run/utmp -p wa -k session -w /var/log/wtmp -p wa -k session -w /var/log/btmp -p wa -k session Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor session initiation information. Example: # printf " -w /var/run/utmp -p wa -k session -w /var/log/wtmp -p wa -k session -w /var/log/btmp -p wa -k session " >> /etc/audit/rules.d/50-session.rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi Page 783 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: AU-3 2. STIG ID: UBTU-20-010279 | RULE ID: SV-238317r991581 | CAT II 3. STIG ID: UBTU-20-010278 | RULE ID: SV-238316r991581 | CAT II 4. STIG ID: UBTU-20-010277 | RULE ID: SV-238315r991581 | CAT II 5. STIG ID: UBTU-22-654195 | RULE ID: SV-260641r991581 | CAT II 6. STIG ID: UBTU-22-654200 | RULE ID: SV-260642r991581 | CAT II 7. STIG ID: UBTU-22-654205 | RULE ID: SV-260643r991581 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 784 Internal Only - General 6.2.3.12 Ensure login and logout events are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor login and logout events. The parameters below track changes to files associated with login/logout events. • /var/log/lastlog - maintain records of the last time a user successfully logged in. • /var/run/faillock - directory maintains records of login failures via the pam_faillock module. Rationale: Monitoring login/logout events could provide a system administrator with information associated with brute force attacks against user logins. Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-w/ \ &&(/\/var\/log\/lastlog/ \ ||/\/var\/run\/faillock/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -w /var/log/lastlog -p wa -k logins -w /var/run/faillock -p wa -k logins Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-w/ \ &&(/\/var\/log\/lastlog/ \ ||/\/var\/run\/faillock/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -w /var/log/lastlog -p wa -k logins -w /var/run/faillock -p wa -k logins Page 785 Internal Only - General Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor login and logout events. Example: # printf " -w /var/log/lastlog -p wa -k logins -w /var/run/faillock -p wa -k logins " >> /etc/audit/rules.d/50-login.rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 786 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 4.9 Log and Alert on Unsuccessful Administrative Account v7 Login ● ● Configure systems to issue a log entry and alert on unsuccessful logins to an administrative account. v7 16.11 Lock Workstation Sessions After Inactivity ● ● ● Automatically lock workstation sessions after a standard period of inactivity. 16.13 Alert on Account Login Behavior Deviation v7 Alert when users deviate from normal login behavior, such as time-of-day, ● workstation location and duration. Page 787 Internal Only - General 6.2.3.13 Ensure file deletion events by users are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the use of system calls associated with the deletion or renaming of files and file attributes. This configuration statement sets up monitoring for: • unlink - remove a file • unlinkat - remove a file attribute • rename - rename a file • renameat rename a file attribute system calls and tags them with the identifier "delete". Rationale: Monitoring these calls from non-privileged users could provide a system administrator with evidence that inappropriate removal of files and file attributes associated with protected files is occurring. While this audit option will look at all events, system administrators will want to look for specific privileged files that are being deleted or altered. Page 788 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -S/ \ &&(/unlink/||/rename/||/unlinkat/||/renameat/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S unlink,unlinkat,rename,renameat -F auid>=1000 - F auid!=unset -k delete -a always,exit -F arch=b32 -S unlink,unlinkat,rename,renameat -F auid>=1000 - F auid!=unset -k delete Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -S/ \ &&(/unlink/||/rename/||/unlinkat/||/renameat/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S rename,unlink,unlinkat,renameat -F auid>=1000 - F auid!=-1 -F key=delete -a always,exit -F arch=b32 -S unlink,rename,unlinkat,renameat -F auid>=1000 - F auid!=-1 -F key=delete Page 789 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor file deletion events by users. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F arch=b64 -S rename,unlink,unlinkat,renameat -F auid>=${UID_MIN} -F auid!=unset -F key=delete -a always,exit -F arch=b32 -S rename,unlink,unlinkat,renameat -F auid>=${UID_MIN} -F auid!=unset -F key=delete " >> /etc/audit/rules.d/50-delete.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-12, SC-7 2. STIG ID: UBTU-20-010267 | Rule ID: SV-238310r991577 | CAT II 3. STIG ID: UBTU-22-654185 | Rule ID: SV-260639r991577 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 790 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 791 Internal Only - General 6.2.3.14 Ensure events that modify the system's Mandatory Access Controls are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor AppArmor, an implementation of mandatory access controls. The parameters below monitor any write access (potential additional, deletion or modification of files in the directory) or attribute changes to the /etc/apparmor/ and /etc/apparmor.d/ directories. Note: If a different Mandatory Access Control method is used, changes to the corresponding directories should be audited. Rationale: Changes to files in the /etc/apparmor/ and /etc/apparmor.d/ directories could indicate that an unauthorized user is attempting to modify access controls and change security contexts, leading to a compromise of the system. Page 792 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # awk '/^ *-w/ \ &&(/\/etc\/apparmor/ \ ||/\/etc\/apparmor.d/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules Verify the output matches: -w /etc/apparmor/ -p wa -k MAC-policy -w /etc/apparmor.d/ -p wa -k MAC-policy Running configuration Run the following command to check loaded rules: # auditctl -l | awk '/^ *-w/ \ &&(/\/etc\/apparmor/ \ ||/\/etc\/apparmor.d/) \ &&/ +-p *wa/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' Verify the output matches: -w /etc/apparmor/ -p wa -k MAC-policy -w /etc/apparmor.d/ -p wa -k MAC-policy Remediation: Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify the system's Mandatory Access Controls. Example: # printf " -w /etc/apparmor/ -p wa -k MAC-policy -w /etc/apparmor.d/ -p wa -k MAC-policy " >> /etc/audit/rules.d/50-MAC-policy.rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 Page 793 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 5.5 Implement Automated Configuration Monitoring Systems v7 Utilize a Security Content Automation Protocol (SCAP) compliant configuration ● ● monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur. Page 794 Internal Only - General 6.2.3.15 Ensure successful and unsuccessful attempts to use the chcon command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the chcon command. Rationale: The chcon command is used to change file security context. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Page 795 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/chcon/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/chcon/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -S all -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=-1 -F key=perm_chng Page 796 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the chcon command. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F path=/usr/bin/chcon -F perm=x -F auid>=${UID_MIN} -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 797 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 798 Internal Only - General 6.2.3.16 Ensure successful and unsuccessful attempts to use the setfacl command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the setfacl command Rationale: This utility sets Access Control Lists (ACLs) of files and directories. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Page 799 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/setfacl/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/setfacl/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -S all -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=-1 -F key=perm_chng Page 800 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the setfacl command. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F path=/usr/bin/setfacl -F perm=x -F auid>=${UID_MIN} -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 801 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 802 Internal Only - General 6.2.3.17 Ensure successful and unsuccessful attempts to use the chacl command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the chacl command. chacl is an IRIX-compatibility command, and is maintained for those users who are familiar with its use from either XFS or IRIX. Rationale: chacl changes the ACL(s) for a file or directory. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Page 803 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/chacl/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_chng Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/chacl/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -S all -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=-1 -F key=perm_chng Page 804 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the chacl command. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F path=/usr/bin/chacl -F perm=x -F auid>=${UID_MIN} -F auid!=unset -k perm_chng " >> /etc/audit/rules.d/50-perm_chng.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 805 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 806 Internal Only - General 6.2.3.18 Ensure successful and unsuccessful attempts to use the usermod command are collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The operating system must generate audit records for successful/unsuccessful uses of the usermod command. Rationale: The usermod command modifies the system account files to reflect the changes that are specified on the command line. Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one. Audit records can be generated from various components within the information system (e.g., module or policy filter). Page 807 Internal Only - General Audit: On disk configuration Run the following command to check the on disk rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/sbin\/usermod/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=unset -k usermod Running configuration Run the following command to check loaded rules: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/sbin\/usermod/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -S all -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=-1 -F key=usermod Page 808 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor successful and unsuccessful attempts to use the usermod command. Example: # { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F path=/usr/sbin/usermod -F perm=x -F auid>=${UID_MIN} -F auid!=unset -k usermod " >> /etc/audit/rules.d/50-usermod.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-2, AU-12, SI-5 Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 809 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.2 Collect Audit Logs v8 Collect audit logs. Ensure that logging, per the enterprise’s audit log ● ● ● management process, has been enabled across enterprise assets. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 810 Internal Only - General 6.2.3.19 Ensure kernel module loading unloading and modification is collected (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Monitor the loading and unloading of kernel modules. All the loading / listing / dependency checking of modules is done by kmod via symbolic links. The following system calls control loading and unloading of modules: • init_module - load a module • finit_module - load a module (used when the overhead of using cryptographically signed modules to determine the authenticity of a module can be avoided) • delete_module - delete a module • query_module - query the kernel for various bits pertaining to modules Any execution of the loading and unloading module programs and system calls will trigger an audit record with an identifier of modules. Rationale: Monitoring the use of all the various ways to manipulate kernel modules could provide system administrators with evidence that an unauthorized change was made to a kernel module, possibly compromising the security of the system. Audit: On disk configuration Run the following script to check the on disk rules: Page 811 Internal Only - General #!/usr/bin/env bash { awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F auid!=unset/||/ -F auid!=-1/||/ -F auid!=4294967295/) \ &&/ -S/ \ &&(/init_module/ \ ||/finit_module/ \ ||/delete_module/ \ ||/query_module/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' /etc/audit/rules.d/*.rules UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/kmod/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" /etc/audit/rules.d/*.rules \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output matches: -a always,exit -F arch=b64 -S init_module,finit_module,delete_module,query_module -F auid>=1000 -F auid!=unset -k kernel_modules -a always,exit -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset - k kernel_modules Running configuration Run the following script to check loaded rules: #!/usr/bin/env bash { auditctl -l | awk '/^ *-a *always,exit/ \ &&/ -F *arch=b(32|64)/ \ &&(/ -F auid!=unset/||/ -F auid!=-1/||/ -F auid!=4294967295/) \ &&/ -S/ \ &&(/init_module/ \ ||/finit_module/ \ ||/delete_module/ \ ||/query_module/) \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)' UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && auditctl -l | awk "/^ *-a *always,exit/ \ &&(/ -F *auid!=unset/||/ -F *auid!=-1/||/ -F *auid!=4294967295/) \ &&/ -F *auid>=${UID_MIN}/ \ &&/ -F *perm=x/ \ &&/ -F *path=\/usr\/bin\/kmod/ \ &&(/ key= *[!-~]* *$/||/ -k *[!-~]* *$/)" \ || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Verify the output includes: Page 812 Internal Only - General -a always,exit -F arch=b64 -S init_module,delete_module,query_module,finit_module -F auid>=1000 -F auid!=-1 -F key=kernel_modules -a always,exit -S all -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=-1 -F key=kernel_modules Symlink audit Run the following script to audit if the symlinks kmod accepts are indeed pointing at it: #!/usr/bin/env bash { a_files=("/usr/sbin/lsmod" "/usr/sbin/rmmod" "/usr/sbin/insmod" "/usr/sbin/modinfo" "/usr/sbin/modprobe" "/usr/sbin/depmod") for l_file in "${a_files[@]}"; do if [ "$(readlink -f "$l_file")" = "$(readlink -f /bin/kmod)" ]; then printf "OK: \"$l_file\"\n" else printf "Issue with symlink for file: \"$l_file\"\n" fi done } Verify the output states OK. If there is a symlink pointing to a different location it should be investigated Page 813 Internal Only - General Remediation: Create audit rules Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor kernel module modification. Example: #!/usr/bin/env bash { UID_MIN=$(awk '/^\s*UID_MIN/{print $2}' /etc/login.defs) [ -n "${UID_MIN}" ] && printf " -a always,exit -F arch=b64 -S init_module,finit_module,delete_module,query_module -F auid>=${UID_MIN} -F auid!=unset -k kernel_modules -a always,exit -F path=/usr/bin/kmod -F perm=x -F auid>=${UID_MIN} -F auid!=unset -k kernel_modules " >> /etc/audit/rules.d/50-kernel_modules.rules || printf "ERROR: Variable 'UID_MIN' is unset.\n" } Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3, CM-6 2. STIG ID: UBTU-20-010296 | RULE ID: SV-238318r991586 | CAT II 3. STIG ID: UBTU-22-654060 | RULE ID: SV-260614r991586 | CAT II Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. System call structure For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimized for performance as per the man page. Page 814 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. Page 815 Internal Only - General 6.2.3.20 Ensure the audit configuration is immutable (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Set system audit so that audit rules cannot be modified with auditctl . Setting the flag "-e 2" forces audit to be put in immutable mode. Audit changes can only be made on system reboot. Note: This setting will require the system to be rebooted to update the active auditd configuration settings. Rationale: In immutable mode, unauthorized users cannot execute changes to the audit system to potentially hide malicious activity and then put the audit rules back. Users would most likely notice a system reboot and that could alert administrators of an attempt to make unauthorized audit changes. Audit: Run the following command and verify output matches: # grep -Ph -- '^\h*-e\h+2\b' /etc/audit/rules.d/*.rules | tail -1 -e 2 Remediation: Edit or create the file /etc/audit/rules.d/99-finalize.rules and add the line -e 2 at the end of the file: Example: # printf '\n%s' "-e 2" >> /etc/audit/rules.d/99-finalize.rules Load audit rules Merge and load the rules into active configuration: # augenrules --load Check if reboot is required. # if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi References: 1. NIST SP 800-53 Rev. 5: AC-3, AU-3, AU-12, MP-2 Page 816 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.2 Activate audit logging v7 Ensure that local logging has been enabled on all systems and networking ● ● ● devices. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 817 Internal Only - General 6.2.3.21 Ensure the running and on disk configuration is the same (Manual) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The Audit system have both on disk and running configuration. It is possible for these configuration settings to differ. Note: Due to the limitations of augenrules and auditctl, it is not absolutely guaranteed that loading the rule sets via augenrules --load will result in all rules being loaded or even that the user will be informed if there was a problem loading the rules. Rationale: Configuration differences between what is currently running and what is on disk could cause unexpected problems or may give a false impression of compliance requirements. Audit: Merged rule sets Ensure that all rules in /etc/audit/rules.d have been merged into /etc/audit/audit.rules: # augenrules --check /usr/sbin/augenrules: No change Should there be any drift, run augenrules --load to merge and load all rules. Remediation: If the rules are not aligned across all three () areas, run the following command to merge and load all rules: # augenrules --load Check if reboot is required. if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then echo "Reboot required to load rules"; fi References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 818 Internal Only - General Additional Information: Potential reboot required If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 8.5 Collect Detailed Audit Logs v8 Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination ● ● addresses, and other useful elements that could assist in a forensic investigation. 6.3 Enable Detailed Logging v7 Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful ● ● elements. Page 819 Internal Only - General 6.2.4 Configure auditd File Access Without the capability to restrict which roles and individuals can select which events are audited, unauthorized personnel may be able to prevent the auditing of critical events. Page 820 Internal Only - General 6.2.4.1 Ensure audit log files mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Page 821 Internal Only - General Audit: Run the following script to verify audit log files are mode 0640 or more restrictive: #!/usr/bin/env bash { l_perm_mask="0137" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then l_maxperm="$(printf '%o' $(( 0777 & ~$l_perm_mask )) )" a_files=() while IFS= read -r -d $'\0' l_file; do [ -e "$l_file" ] && a_files+=("$l_file") done < <(find "$l_audit_log_directory" -maxdepth 1 -type f -perm /"$l_perm_mask" -print0) if (( "${#a_files[@]}" > 0 )); then for l_file in "${a_files[@]}"; do l_file_mode="$(stat -Lc '%#a' "$l_file")" echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"$l_file\" is mode: \"$l_file_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" done else echo -e "\n- Audit Result:\n ** PASS **\n - All files in \"$l_audit_log_directory\" are mode: \"$l_maxperm\" or more restrictive" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"/etc/audit/auditd.conf\" not found.\n - ** Verify auditd is installed **" fi } Remediation: Run the following command to remove more permissive mode than 0640 from audit log files: # [ -f /etc/audit/auditd.conf ] && find "$(dirname $(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs))" -type f -perm /0137 -exec chmod u-x,g-wx,o-rwx {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 822 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 823 Internal Only - General 6.2.4.2 Ensure audit log files owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Audit: Run the following script to verify audit log files are owned by the root user: #!/usr/bin/env bash { l_output="" l_output2="" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then while IFS= read -r -d $'\0' l_file; do l_output2="$l_output2\n - File: \"$l_file\" is owned by user: \"$(stat -Lc '%U' "$l_file")\"\n (should be owned by user: \"root\")\n" done < <(find "$l_audit_log_directory" -maxdepth 1 -type f ! -user root -print0) else l_output2="$l_output2\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else l_output2="$l_output2\n - File: \"/etc/audit/auditd.conf\" not found.\n - ** Verify auditd is installed **" fi if [ -z "$l_output2" ]; then l_output="$l_output\n - All files in \"$l_audit_log_directory\" are owned by user: \"root\"\n" echo -e "\n- Audit Result:\n ** PASS **\n - * Correctly configured * :$l_output" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :$l_output2\n" fi } Page 824 Internal Only - General Remediation: Run the following command to configure the audit log files to be owned by the root user: # [ -f /etc/audit/auditd.conf ] && find "$(dirname $(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs))" -type f ! -user root -exec chown root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 825 Internal Only - General 6.2.4.3 Ensure audit log files group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit log files contain information about the system and system activity. Rationale: Access to audit records can reveal system and configuration data to attackers, potentially compromising its confidentiality. Audit: Run the following command to verify log_group parameter is set to either adm or root in /etc/audit/auditd.conf: # grep -Piws -- '^\h*log_group\h*=\h*\H+\b' /etc/audit/auditd.conf | grep - Pvi -- '(adm)' Nothing should be returned Using the path of the directory containing the audit logs, verify audit log files are owned by the "root" or "adm" group by running the following script: #!/usr/bin/env bash { if [ -e /etc/audit/auditd.conf ]; then l_fpath="$(dirname "$(awk -F "=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs)")" find -L "$l_fpath" -maxdepth 1 -not -path "$l_fpath"/lost+found -type f \( ! -group root -a ! -group adm \) -exec ls -l {} + fi } Nothing should be returned Page 826 Internal Only - General Remediation: Run the following command to configure the audit log files to be group owned by adm: # find $(dirname $(awk -F"=" '/^\s*log_file/ {print $2}' /etc/audit/auditd.conf | xargs)) -type f \( ! -group adm -a ! -group root \) -exec chgrp adm {} + Run the following command to set the log_group parameter in the audit configuration file to log_group = adm: # sed -ri 's/^\s*#?\s*log_group\s*=\s*\S+(\s*#.*)?.*$/log_group = adm\1/' /etc/audit/auditd.conf Run the following command to restart the audit daemon to reload the configuration file: # systemctl restart auditd References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 827 Internal Only - General 6.2.4.4 Ensure the audit log file directory mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: The audit log directory contains audit log files. Rationale: Audit information includes all information including: audit records, audit settings and audit reports. This information is needed to successfully audit system activity. This information must be protected from unauthorized modification or deletion. If this information were to be compromised, forensic analysis and discovery of the true source of potentially malicious system activity is impossible to achieve. Audit: Run the following script to verify the audit log directory is mode 0750 or more restrictive: #!/usr/bin/env bash { l_perm_mask="0027" if [ -e "/etc/audit/auditd.conf" ]; then l_audit_log_directory="$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" if [ -d "$l_audit_log_directory" ]; then l_maxperm="$(printf '%o' $(( 0777 & ~$l_perm_mask )) )" l_directory_mode="$(stat -Lc '%#a' "$l_audit_log_directory")" if [ $(( $l_directory_mode & $l_perm_mask )) -gt 0 ]; then echo -e "\n- Audit Result:\n ** FAIL **\n - Directory: \"$l_audit_log_directory\" is mode: \"$l_directory_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" else echo -e "\n- Audit Result:\n ** PASS **\n - Directory: \"$l_audit_log_directory\" is mode: \"$l_directory_mode\"\n (should be mode: \"$l_maxperm\" or more restrictive)\n" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - Log file directory not set in \"/etc/audit/auditd.conf\" please set log file directory" fi else echo -e "\n- Audit Result:\n ** FAIL **\n - File: \"/etc/audit/auditd.conf\" not found\n - ** Verify auditd is installed **" fi } Page 828 Internal Only - General Remediation: Run the following command to configure the audit log directory to have a mode of "0750" or less permissive: # chmod g-w,o-rwx "$(dirname "$(awk -F= '/^\s*log_file\s*/{print $2}' /etc/audit/auditd.conf | xargs)")" Default Value: 750 References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 829 Internal Only - General 6.2.4.5 Ensure audit configuration files mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following script to verify that the audit configuration files are mode 0640 or more restrictive: #!/usr/bin/env bash { l_output="" l_output2="" l_perm_mask="0137" l_maxperm="$( printf '%o' $(( 0777 & ~$l_perm_mask )) )" while IFS= read -r -d $'\0' l_fname; do l_mode=$(stat -Lc '%#a' "$l_fname") if [ $(( "$l_mode" & "$l_perm_mask" )) -gt 0 ]; then l_output2="$l_output2\n - file: \"$l_fname\" is mode: \"$l_mode\" (should be mode: \"$l_maxperm\" or more restrictive)" fi done < <(find /etc/audit/ -type f \( -name "*.conf" -o -name '*.rules' \) -print0) if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n - All audit configuration files are mode: \"$l_maxperm\" or more restrictive" else echo -e "\n- Audit Result:\n ** FAIL **\n$l_output2" fi } Page 830 Internal Only - General Remediation: Run the following command to remove more permissive mode than 0640 from the audit configuration files: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) -exec chmod u-x,g-wx,o-rwx {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 831 Internal Only - General 6.2.4.6 Ensure audit configuration files owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following command to verify that the audit configuration files are owned by the root user: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -user root Nothing should be returned Remediation: Run the following command to change ownership to root user: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -user root -exec chown root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 832 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 833 Internal Only - General 6.2.4.7 Ensure audit configuration files group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit configuration files control auditd and what events are audited. Rationale: Access to the audit configuration files could allow unauthorized personnel to prevent the auditing of critical events. Misconfigured audit configuration files may prevent the auditing of critical events or impact the system's performance by overwhelming the audit log. Misconfiguration of the audit configuration files may also make it more difficult to establish and investigate events relating to an incident. Audit: Run the following command to verify that the audit configuration files are owned by the group root: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -group root Nothing should be returned Remediation: Run the following command to change group to root: # find /etc/audit/ -type f \( -name '*.conf' -o -name '*.rules' \) ! -group root -exec chgrp root {} + References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 834 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 835 Internal Only - General 6.2.4.8 Ensure audit tools mode is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following script to verify the audit tools are mode 0755 or more restrictive: #!/usr/bin/env bash { l_output="" l_output2="" l_perm_mask="0022" l_maxperm="$( printf '%o' $(( 0777 & ~$l_perm_mask )) )" a_audit_tools=("/sbin/auditctl" "/sbin/aureport" "/sbin/ausearch" "/sbin/autrace" "/sbin/auditd" "/sbin/augenrules") for l_audit_tool in "${a_audit_tools[@]}"; do l_mode="$(stat -Lc '%#a' "$l_audit_tool")" if [ $(( "$l_mode" & "$l_perm_mask" )) -gt 0 ]; then l_output2="$l_output2\n - Audit tool \"$l_audit_tool\" is mode: \"$l_mode\" and should be mode: \"$l_maxperm\" or more restrictive" else l_output="$l_output\n - Audit tool \"$l_audit_tool\" is correctly configured to mode: \"$l_mode\"" fi done if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n ** PASS **\n - * Correctly configured * :$l_output" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :$l_output2\n" [ -n "$l_output" ] && echo -e "\n - * Correctly configured * :\n$l_output\n" fi unset a_audit_tools } Page 836 Internal Only - General Remediation: Run the following command to remove more permissive mode from the audit tools: # chmod go-w /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 837 Internal Only - General 6.2.4.9 Ensure audit tools owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following command to verify the audit tools are owned by the root user: # stat -Lc "%n %U" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/augenrules | awk '$2 != "root" {print}' Nothing should be returned Remediation: Run the following command to change the owner of the audit tools to the root user: # chown root /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 838 Internal Only - General 6.2.4.10 Ensure audit tools group owner is configured (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting audit information includes identifying and protecting the tools used to view and manipulate log data. Protecting audit tools is necessary to prevent unauthorized operation on audit information. Audit: Run the following command to verify the audit tools are owned by the group root # stat -Lc "%n %G" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/augenrules | awk '$2 != "root" {print}' Nothing should be returned Remediation: Run the following command to change group ownership to the group root: # chgrp root /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/augenrules References: 1. NIST SP 800-53 Rev. 5: AU-3 Page 839 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 840 Internal Only - General 6.3 Configure Filesystem Integrity Checking AIDE is a file integrity checking tool. While it cannot prevent intrusions, it can detect unauthorized changes to configuration files by alerting when the files are changed. When setting up AIDE, decide internally what the site policy will be concerning integrity checking. Review the AIDE quick start guide and AIDE documentation before proceeding. Note: - IF - another local site approved solution is used, and configured to provide the capabilities covered by AIDE in this section, this section may be skipped. Page 841 Internal Only - General 6.3.1 Ensure AIDE is installed (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: AIDE takes a snapshot of filesystem state including modification times, permissions, and file hashes which can then be used to compare against the current state of the filesystem to detect modifications to the system. Rationale: By monitoring the filesystem state compromised files can be detected to prevent or limit the exposure of accidental or malicious misconfigurations or modified binaries. Audit: Run the following command to verify aide is installed: # dpkg-query -s aide &>/dev/null && echo "aide is installed" aide is installed Run the following command to verify aide-common is installed: # dpkg-query -s aide-common &>/dev/null && echo "aide-common is installed" aide-common is installed Remediation: Install AIDE using the appropriate package manager or manual installation: # apt install aide aide-common Configure AIDE as appropriate for your environment. Consult the AIDE documentation for options. Run the following commands to initialize AIDE: # aideinit # mv /var/lib/aide/aide.db.new /var/lib/aide/aide.db References: 1. NIST SP 800-53 Rev. 5: AU-2 Additional Information: The prelinking feature can interfere with AIDE because it alters binaries to speed up their start up times. Run prelink -ua to restore the binaries to their prelinked state, thus avoiding false positives from AIDE. Page 842 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 843 Internal Only - General 6.3.2 Ensure filesystem integrity is regularly checked (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Periodic checking of the filesystem integrity is needed to detect changes to the filesystem. Rationale: Periodic file checking allows the system administrator to determine on a regular basis if critical files have been changed in an unauthorized fashion. Audit: Run the following commands to verify a cron job scheduled to run the aide check. # grep -Prs '^([^#\n\r]+\h+)?(\/usr\/s?bin\/|^\h*)aide(\.wrapper)?\h+(-- (check|update)|([^#\n\r]+\h+)?\$AIDEARGS)\b' /etc/cron.* /etc/crontab /var/spool/cron/ Ensure a cron job in compliance with site policy is returned. - OR - Run the following commands to verify that aidecheck.service and aidecheck.timer are enabled and aidecheck.timer is running # systemctl is-enabled aidecheck.service # systemctl is-enabled aidecheck.timer # systemctl status aidecheck.timer Page 844 Internal Only - General Remediation: If cron will be used to schedule and run aide check: Run the following command: # crontab -u root -e Add the following line to the crontab: 0 5 * * * /usr/bin/aide.wrapper --config /etc/aide/aide.conf --update - OR - If aidecheck.service and aidecheck.timer will be used to schedule and run aide check: Create or edit the file /etc/systemd/system/aidecheck.service and add the following lines: [Unit] Description=Aide Check [Service] Type=simple ExecStart=/usr/bin/aide.wrapper --config /etc/aide/aide.conf --update [Install] WantedBy=multi-user.target Create or edit the file /etc/systemd/system/aidecheck.timer and add the following lines: [Unit] Description=Aide check every day at 5AM [Timer] OnCalendar=*-*-* 05:00:00 Unit=aidecheck.service [Install] WantedBy=multi-user.target Run the following commands: # chown root:root /etc/systemd/system/aidecheck.* # chmod 0644 /etc/systemd/system/aidecheck.* # systemctl daemon-reload # systemctl enable aidecheck.service # systemctl --now enable aidecheck.timer References: 1. https://github.com/konstruktoid/hardening/blob/master/config/aidecheck.service 2. https://github.com/konstruktoid/hardening/blob/master/config/aidecheck.timer Page 845 Internal Only - General Additional Information: The checking in this recommendation occurs every day at 5am. Alter the frequency and time of the checks in compliance with site policy systemd timers, timer file aidecheck.timer and service file aidecheck.service, have been included as an optional alternative to using cron Ubuntu advises using /usr/bin/aide.wrapper rather than calling /usr/bin/aide directly in order to protect the database and prevent conflicts CIS Controls: Controls Control IG 1 IG 2 IG 3 Version v8 3.14 Log Sensitive Data Access ● Log sensitive data access, including modification and disposal. 14.9 Enforce Detail Logging for Access or Changes to Sensitive Data v7 Enforce detailed audit logging for access to sensitive data or changes to ● sensitive data (utilizing tools such as File Integrity Monitoring or Security Information and Event Monitoring). Page 846 Internal Only - General 6.3.3 Ensure cryptographic mechanisms are used to protect the integrity of audit tools (Automated) Profile Applicability: • Level 2 - Server • Level 2 - Workstation Description: Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators. Rationale: Protecting the integrity of the tools used for auditing purposes is a critical step toward ensuring the integrity of audit information. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity. Attackers may replace the audit tools or inject code into the existing tools with the purpose of providing the capability to hide or erase system activity from the audit logs. Audit tools should be cryptographically signed in order to provide the capability to identify when the audit tools have been modified, manipulated, or replaced. An example is a checksum hash of the file or files. Audit: Verify that Advanced Intrusion Detection Environment (AIDE) is properly configured . Run the following script to verify: • AIDE is configured to use cryptographic mechanisms to protect the integrity of audit tools: • The following audit tool files include the options "p, i, n, u, g, s, b, acl, xattrs and sha512" o auditctl o auditd o ausearch o aureport o autrace o augenrules Page 847 Internal Only - General #!/usr/bin/env bash { a_output=();a_output2=();a_output3=();a_parlist=() l_systemd_analyze="$(readlink -e /bin/systemd-analyze || readlink -e /usr/bin/systemd-analyze)" a_audit_files=("auditctl" "auditd" "ausearch" "aureport" "autrace" "augenrules") f_parameter_chk() { for l_tool_file in "${a_parlist[@]}"; do if grep -Pq -- '\b'"$l_tool_file"'\b' <<< "${!A_out[*]}"; then for l_string in "${!A_out[@]}"; do l_check="$(grep -Po -- '^\h*(\/usr)?\/sbin\/'"$l_tool_file"'\b' <<< "$l_string")" if [ -n "$l_check" ]; then l_fname="$(printf '%s' "${A_out[$l_string]}")" [ "$l_check" != "$(readlink -f "$l_check")" ] && \ a_output3+=(" - \"$l_check\" should be updated to: \"$(readlink -e "$l_check")\"" " in: \"$l_fname\"") a_missing=() for l_var in "${a_items[@]}"; do if ! grep -Pq -- "\b$l_var\b" <<< "$l_string"; then a_missing+=("\"$l_var\"") fi done if [ "${#a_missing[@]}" -gt 0 ]; then a_output2+=(" - Option(s): ( ${a_missing[*]} ) are missing from: \"$l_tool_file\" in: \"$l_fname\"") else a_output+=(" - Audit tool file \"$l_tool_file\" exists as:" " \"$l_string\"" " in the configuration file: \"$l_fname\"") fi fi done else a_output2+=(" - Audit tool file \"$l_tool_file\" doesn't exist in an AIDE configuration file") fi done } f_aide_conf() { l_config_file="$(readlink -e /etc/aide/aide.conf || readlink -e /etc/aide.conf)" if [ -f "$l_config_file" ]; then a_items=("p" "i" "n" "u" "g" "s" "b" "acl" "xattrs" "sha512") declare -A A_out while IFS= read -r l_out; do if grep -Pq -- '^\h*\#\h*\/[^#\n\r]+\.conf\b' <<< "$l_out"; then l_file="${l_out//# /}" else for i in "${a_parlist[@]}"; do grep -Pq -- '^\h*(\/usr)?\/sbin\/'"$i"'\b' <<< "$l_out" && A_out+=(["$l_out"]="$l_file") done fi Page 848 Internal Only - General done < <("$l_systemd_analyze" cat-config "$l_config_file" | grep - Pio '^\h*([^#\n\r]+|#\h*\/[^#\n\r\h]+\.conf\b)') if [ "${#A_out[@]}" -gt 0 ]; then f_parameter_chk else a_output2+=(" - No audit tool files are configured in an AIDE configuration file") fi else a_output2+=(" - AIDE configuration file not found." " Please verify AIDE is installed on the system") fi } for l_audit_file in "${a_audit_files[@]}"; do if [ -f "$(readlink -f "/sbin/$l_audit_file")" ]; then a_parlist+=("$l_audit_file") else a_output+=(" - Audit tool file \"$(readlink -f "/sbin/$l_audit_file")\" doesn't exist") fi done [ "${#a_parlist[@]}" -gt 0 ] && f_aide_conf if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " ** WARNING **" "${a_output3[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " * Reasons for audit failure *" "${a_output2[@]}" "" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " ** WARNING **" "${a_output3[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Note: The script is written to read the "winning" configuration setting, to include any configuration settings in files included as part of the @@x_include setting. Page 849 Internal Only - General Remediation: Run the following command to determine the absolute path to the non-symlinked version on the audit tools: # readlink -e /sbin The output will be either /usr/sbin - OR - /sbin. Ensure the correct path is used. Edit /etc/aide/aide.conf and add or update the following selection lines replacing with the correct path returned in the command above: # Audit Tools /auditctl p+i+n+u+g+s+b+acl+xattrs+sha512 /auditd p+i+n+u+g+s+b+acl+xattrs+sha512 /ausearch p+i+n+u+g+s+b+acl+xattrs+sha512 /aureport p+i+n+u+g+s+b+acl+xattrs+sha512 /autrace p+i+n+u+g+s+b+acl+xattrs+sha512 /augenrules p+i+n+u+g+s+b+acl+xattrs+sha512 Example # printf '%s\n' "" "# Audit Tools" "$(readlink -e /sbin/auditctl) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -e /sbin/auditd) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -e /sbin/ausearch) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -e /sbin/aureport) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -e /sbin/autrace) p+i+n+u+g+s+b+acl+xattrs+sha512" "$(readlink -e /sbin/augenrules) p+i+n+u+g+s+b+acl+xattrs+sha512" >> "$(readlink -e /etc/aide/aide.conf || readlink -e /etc/aide.conf)" Note: - IF - /etc/aide/aide.conf includes a @@x_include statement: Example: @@x_include /etc/aide/aide.conf.d ^[a-zA-Z0-9_-]+$ • @@x_include FILE • @@x_include DIRECTORY REGEX o @x_include is identical to @@include, except that if a config file is executable it is run and the output is used as config. o If the executable file exits with status greater than zero or writes to stderr aide stops with an error. o For security reasons DIRECTORY and each executable config file must be owned by the current user and must not be group or world-writable. References: 1. AIDE.CONF(5) 2. STIG ID: UBTU-20-010205 | RULE ID: SV-238303r991567 | CAT II 3. STIG ID: UBTU-22-651030 | RULE ID: SV-260586r1044779 | CAT II 4. STIG ID: UBTU-24-90890 | RULE ID: SV-270831r1066982 | CAT II Page 850 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped 7 System Maintenance Recommendations in this section are intended as maintenance and are intended to be checked on a frequent basis to ensure system stability. Many recommendations do not have quick remediations and require investigation into the cause and best fix available and may indicate an attempted breach of system security. Page 851 Internal Only - General 7.1 Configure system file and directory access This section provides guidance on securing aspects of system files and directories. Page 852 Internal Only - General 7.1.1 Ensure access to /etc/passwd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/passwd file contains user account information that is used by many system utilities and therefore must be readable for these utilities to operate. Rationale: It is critical to ensure that the /etc/passwd file is protected from unauthorized write access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/passwd is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/passwd Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/passwd: # chmod u-x,go-wx /etc/passwd # chown root:root /etc/passwd Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 853 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 854 Internal Only - General 7.1.2 Ensure access to /etc/passwd- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/passwd- file contains backup user account information. Rationale: It is critical to ensure that the /etc/passwd- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/passwd- is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: { %g/ %G)' /etc/passwd- Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/passwd-: # chmod u-x,go-wx /etc/passwd- # chown root:root /etc/passwd- Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: { 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 855 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 856 Internal Only - General 7.1.3 Ensure access to /etc/group is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/group file contains a list of all the valid groups defined in the system. The command below allows read/write access for root and read access for everyone else. Rationale: The /etc/group file needs to be protected from unauthorized changes by non- privileged users, but needs to be readable as this information is used with many non- privileged programs. Audit: Run the following command to verify /etc/group is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/group Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/group: # chmod u-x,go-wx /etc/group # chown root:root /etc/group Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 857 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 858 Internal Only - General 7.1.4 Ensure access to /etc/group- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/group- file contains a backup list of all the valid groups defined in the system. Rationale: It is critical to ensure that the /etc/group- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/group- is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/group- Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/group-: # chmod u-x,go-wx /etc/group- # chown root:root /etc/group- Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 859 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 860 Internal Only - General 7.1.5 Ensure access to /etc/shadow is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/shadow file is used to store the information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert the user accounts. Audit: Run the following command to verify /etc/shadow is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or ({GID}/ shadow): # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/shadow to root and group to either root or shadow: # chown root:shadow /etc/shadow -OR- # chown root:root /etc/shadow Run the following command to remove excess permissions form /etc/shadow: # chmod u-x,g-wx,o-rwx /etc/shadow Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 861 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 862 Internal Only - General 7.1.6 Ensure access to /etc/shadow- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/shadow- file is used to store backup information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: It is critical to ensure that the /etc/shadow- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/shadow- is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow- Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/shadow- to root and group to either root or shadow: # chown root:shadow /etc/shadow- -OR- # chown root:root /etc/shadow- Run the following command to remove excess permissions form /etc/shadow-: # chmod u-x,g-wx,o-rwx /etc/shadow- Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 863 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 864 Internal Only - General 7.1.7 Ensure access to /etc/gshadow is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/gshadow file is used to store the information about groups that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: If attackers can gain read access to the /etc/gshadow file, they can easily run a password cracking program against the hashed password to break it. Other security information that is stored in the /etc/gshadow file (such as group administrators) could also be useful to subvert the group. Audit: Run the following command to verify /etc/gshadow is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or `{GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/gshadow Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/gshadow to root and group to either root or shadow: # chown root:shadow /etc/gshadow -OR- # chown root:root /etc/gshadow Run the following command to remove excess permissions form /etc/gshadow: # chmod u-x,g-wx,o-rwx /etc/gshadow Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 865 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 866 Internal Only - General 7.1.8 Ensure access to /etc/gshadow- is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The /etc/gshadow- file is used to store backup information about groups that is critical to the security of those accounts, such as the hashed password and other security information. Rationale: It is critical to ensure that the /etc/gshadow- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/gshadow- is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/gshadow- Example: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) Remediation: Run one of the following commands to set ownership of /etc/gshadow- to root and group to either root or shadow: # chown root:shadow /etc/gshadow- -OR- # chown root:root /etc/gshadow- Run the following command to remove excess permissions form /etc/gshadow-: # chmod u-x,g-wx,o-rwx /etc/gshadow- Default Value: Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow) References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 Page 867 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 868 Internal Only - General 7.1.9 Ensure access to /etc/shells is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: /etc/shells is a text file which contains the full pathnames of valid login shells. This file is consulted by chsh and available to be queried by other programs. Rationale: It is critical to ensure that the /etc/shells file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following command to verify /etc/shells is mode 644 or more restrictive, Uid is 0/root and Gid is 0/root: # stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shells Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/shells: # chmod u-x,go-wx /etc/shells # chown root:root /etc/shells Default Value: Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 Page 869 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 870 Internal Only - General 7.1.10 Ensure access to /etc/security/opasswd is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: /etc/security/opasswd and it's backup /etc/security/opasswd.old hold user's previous passwords if pam_unix or pam_pwhistory is in use on the system Rationale: It is critical to ensure that /etc/security/opasswd is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions. Audit: Run the following commands to verify /etc/security/opasswd and /etc/security/opasswd.old are mode 600 or more restrictive, Uid is 0/root and Gid is 0/root if they exist: # [ -e "/etc/security/opasswd" ] && stat -Lc '%n Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/security/opasswd /etc/security/opasswd Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) -OR- Nothing is returned # [ -e "/etc/security/opasswd.old" ] && stat -Lc '%n Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/security/opasswd.old /etc/security/opasswd.old Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) -OR- Nothing is returned Page 871 Internal Only - General Remediation: Run the following commands to remove excess permissions, set owner, and set group on /etc/security/opasswd and /etc/security/opasswd.old is they exist: # [ -e "/etc/security/opasswd" ] && chmod u-x,go-rwx /etc/security/opasswd # [ -e "/etc/security/opasswd" ] && chown root:root /etc/security/opasswd # [ -e "/etc/security/opasswd.old" ] && chmod u-x,go-rwx /etc/security/opasswd.old # [ -e "/etc/security/opasswd.old" ] && chown root:root /etc/security/opasswd.old Default Value: /etc/security/opasswd Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) References: 1. NIST SP 800-53 Rev. 5: AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 872 Internal Only - General 7.1.11 Ensure world writable files and directories are secured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: World writable files are the least secure. Data in world-writable files can be modified and compromised by any user on the system. World writable files may also indicate an incorrectly written script or program that could potentially be the cause of a larger compromise to the system's integrity. See the chmod(2) man page for more information. Setting the sticky bit on world writable directories prevents users from deleting or renaming files in that directory that are not owned by them. Rationale: Data in world-writable files can be modified and compromised by any user on the system. World writable files may also indicate an incorrectly written script or program that could potentially be the cause of a larger compromise to the system's integrity. This feature prevents the ability to delete or rename files in world writable directories (such as /tmp ) that are owned by another user. Page 873 Internal Only - General Audit: Run the following script to verify: • No world writable files exist • No world writable directories without the sticky bit exist #!/usr/bin/env bash { a_output=() a_output2=() a_file=() a_dir=() l_smask='01000' l_exclude="nfs|proc|cifs|smb|vfat|iso9660|efivarfs|selinuxfs|ncpfs" l_exclude2="\/run|\/tmp|\/var\/tmp" a_path=(-path "*/containers/storage/*" -o -path "*/containerd/*" -o -path "*/kubelet/*" -o -path "/sys/*" -o -path "/snap/*" -o -path "/boot/efi/*") while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then [ -f "$l_file" ] && a_file+=("$l_file") if [ -d "$l_file" ]; then l_mode="$(stat -Lc '%#a' "$l_file")" [ ! $(( $l_mode & $l_smask )) -gt 0 ] && a_dir+=("$l_file") fi fi done < <(find "$l_mount" -mount -xdev \( "${a_path[@]}" \) \ -prune -o \( -type f -o -type d \) -perm -0002 -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | \ awk '($1 !~ /^\s*('"$l_exclude"')/ && $2 !~ /^('"$l_exclude2"')(\/|$)/){print $2}') if [ "${#a_file[@]}" -le 0 ]; then printf '%s\n' "" " - No world writable files exist on the local filesystem." else printf '%s\n' "" " - There are \"${#a_file[@]}\" World writable files on the system." \ " - The following is a list of World writable files:" \ "${a_file[@]}" " - end of list" fi if [ "${#a_dir[@]}" -le 0 ]; then printf '%s\n' "" \ " - Sticky bit is set on world writable directories on the local filesystem." else printf '%s\n' "" " - There are \"${#a_dir[@]}\" World writable directories" \ " without the sticky bit on the system." \ " - The following is a list of World writable directories without the sticky bit:" \ "${a_dir[@]}" " - end of list" fi } Note: On systems with a large number of files and/or directories, this audit may be a long running process Page 874 Internal Only - General Remediation: • World Writable Files: o It is recommended that write access is removed from other with the command ( chmod o-w ), but always consult relevant vendor documentation to avoid breaking any application dependencies on a given file. • World Writable Directories: o Set the sticky bit on all world writable directories with the command ( chmod a+t ) Run the following script to: • Remove other write permission from any world writable files • Add the sticky bit to all world writable directories #!/usr/bin/env bash { l_smask='01000' a_file=() a_dir=() a_path=(-path "*/containers/storage/*" -o -path "*/containerd/*" -o -path "*/kubelet/*" -o -path "/sys/*" -o -path "/snap/*" -o -path "/boot/efi/*") l_exclude="nfs|proc|cifs|smb|vfat|iso9660|efivarfs|selinuxfs|ncpfs" l_exclude2="\/run|\/tmp|\/var\/tmp" while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do l_mode="$(stat -Lc '%#a' "$l_file" 2>/dev/null)" if [ -f "$l_file" ]; then # Remove excess permissions from WW files printf '%s\n' "" " - File: \"$l_file\" is mode: \"$l_mode\"" \ " - removing write permission on \"$l_file\" from \"other\"" chmod o-w "$l_file" fi if [ -d "$l_file" ]; then # Add sticky bit if [ ! $(( $l_mode & $l_smask )) -gt 0 ]; then printf '%s\n' "" " - Directory: \"$l_file\" is mode: \"$l_mode\"" \ " and doesn't have the sticky bit set" \ " - Adding the sticky bit" chmod a+t "$l_file" fi fi done < <(find "$l_mount" -mount -xdev \( "${a_path[@]}" \) \ -prune -o \( -type f -o -type d \) -perm -0002 -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | \ awk '($1 !~ /^\s*('"$l_exclude"')/ && $2 !~ /^('"$l_exclude2"')(\/|$)/){print $2}') } References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 2. STIG ID: UBTU-20-010411 | Rule ID: SV-238332r958524 | CAT || 3. STIG ID: UBTU-22-232145 | Rule ID: SV-260513r958524 | CAT || Page 875 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 876 Internal Only - General 7.1.12 Ensure no files or directories without an owner and a group exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Administrators may delete users or groups from the system and neglect to remove all files and/or directories owned by those users or groups. Rationale: A new user or group who is assigned a deleted user's user ID or group ID may then end up "owning" a deleted user or group's files, and thus have more access on the system than was intended. Audit: Run the following script to verify no unowned or ungrouped files or directories exist: Page 877 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" a_nouser=(); a_nogroup=() # Initialize arrays a_path=(! -path "/run/user/*" -a ! -path "/proc/*" -a ! -path "*/containerd/*" -a ! -path "*/kubelet/pods/*" -a ! -path "*/kubelet/plugins/*" -a ! -path "/sys/fs/cgroup/memory/*" -a ! -path "/var/*/private/*") while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then while IFS=: read -r l_user l_group; do [ "$l_user" = "UNKNOWN" ] && a_nouser+=("$l_file") [ "$l_group" = "UNKNOWN" ] && a_nogroup+=("$l_file") done < <(stat -Lc '%U:%G' "$l_file") fi done < <(find "$l_mount" -xdev \( "${a_path[@]}" \) \( -type f -o -type d \) \( -nouser -o -nogroup \) -print0 2> /dev/null) done < <(findmnt -Dkerno fstype,target | awk '($1 !~ /^\s*(nfs|proc|smb|vfat|iso9660|efivarfs|selinuxfs)/ && $2 !~ /^\/run\/user\//){print $2}') if ! (( ${#a_nouser[@]} > 0 )); then l_output="$l_output\n - No files or directories without a owner exist on the local filesystem." else l_output2="$l_output2\n - There are \"$(printf '%s' "${#a_nouser[@]}")\" unowned files or directories on the system.\n - The following is a list of unowned files and/or directories:\n$(printf '%s\n' "${a_nouser[@]}")\n - end of list" fi if ! (( ${#a_nogroup[@]} > 0 )); then l_output="$l_output\n - No files or directories without a group exist on the local filesystem." else l_output2="$l_output2\n - There are \"$(printf '%s' "${#a_nogroup[@]}")\" ungrouped files or directories on the system.\n - The following is a list of ungrouped files and/or directories:\n$(printf '%s\n' "${a_nogroup[@]}")\n - end of list" fi unset a_path; unset a_arr ; unset a_nouser; unset a_nogroup # Remove arrays if [ -z "$l_output2" ]; then # If l_output2 is empty, we pass echo -e "\n- Audit Result:\n ** PASS **\n - * Correctly configured * :\n$l_output\n" else echo -e "\n- Audit Result:\n ** FAIL **\n - * Reasons for audit failure * :\n$l_output2" [ -n "$l_output" ] && echo -e "\n- * Correctly configured * :\n$l_output\n" fi } Note: On systems with a large number of files and/or directories, this audit may be a long running process Page 878 Internal Only - General Remediation: Remove or set ownership and group ownership of these files and/or directories to an active user on the system as appropriate. References: 1. NIST SP 800-53 Rev. 5: AC-3. MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 879 Internal Only - General 7.1.13 Ensure SUID and SGID files are reviewed (Manual) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The owner of a file can set the file's permissions to run with the owner's or group's permissions, even if the user running the program is not the owner or a member of the group. The most common reason for a SUID or SGID program is to enable users to perform functions (such as changing their password) that require root privileges. Rationale: There are valid reasons for SUID and SGID programs, but it is important to identify and review such programs to ensure they are legitimate. Review the files returned by the action in the audit section and check to see if system binaries have a different checksum than what from the package. This is an indication that the binary may have been replaced. Audit: Run the following script to generate a list of SUID and SGID files: Page 880 Internal Only - General #!/usr/bin/env bash { l_output="" l_output2="" a_suid=(); a_sgid=() # initialize arrays while IFS= read -r l_mount; do while IFS= read -r -d $'\0' l_file; do if [ -e "$l_file" ]; then l_mode="$(stat -Lc '%#a' "$l_file")" [ $(( $l_mode & 04000 )) -gt 0 ] && a_suid+=("$l_file") [ $(( $l_mode & 02000 )) -gt 0 ] && a_sgid+=("$l_file") fi done < <(find "$l_mount" -xdev -type f \( -perm -2000 -o -perm -4000 \) -print0 2>/dev/null) done < <(findmnt -Dkerno fstype,target,options | awk '($1 !~ /^\s*(nfs|proc|smb|vfat|iso9660|efivarfs|selinuxfs)/ && $2 !~ /^\/run\/user\// && $3 !~/noexec/ && $3 !~/nosuid/) {print $2}') if ! (( ${#a_suid[@]} > 0 )); then l_output="$l_output\n - No executable SUID files exist on the system" else l_output2="$l_output2\n - List of \"$(printf '%s' "${#a_suid[@]}")\" SUID executable files:\n$(printf '%s\n' "${a_suid[@]}")\n - end of list -\n" fi if ! (( ${#a_sgid[@]} > 0 )); then l_output="$l_output\n - No SGID files exist on the system" else l_output2="$l_output2\n - List of \"$(printf '%s' "${#a_sgid[@]}")\" SGID executable files:\n$(printf '%s\n' "${a_sgid[@]}")\n - end of list -\n" fi [ -n "$l_output2" ] && l_output2="$l_output2\n- Review the preceding list(s) of SUID and/or SGID files to\n- ensure that no rogue programs have been introduced onto the system.\n" unset a_arr; unset a_suid; unset a_sgid # Remove arrays # If l_output2 is empty, Nothing to report if [ -z "$l_output2" ]; then echo -e "\n- Audit Result:\n$l_output\n" else echo -e "\n- Audit Result:\n$l_output2\n" [ -n "$l_output" ] && echo -e "$l_output\n" fi } Note: on systems with a large number of files, this may be a long running process Page 881 Internal Only - General Remediation: Ensure that no rogue SUID or SGID programs have been introduced into the system. Review the files returned by the action in the Audit section and confirm the integrity of these binaries. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5, AC-3, MP-2 CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 882 Internal Only - General 7.2 Local User and Group Settings This section provides guidance on securing aspects of the local users and groups. Note: The recommendations in this section check local users and groups. Any users or groups from other sources such as LDAP will not be audited. In a domain environment similar checks should be performed against domain users and groups. Page 883 Internal Only - General 7.2.1 Ensure accounts in /etc/passwd use shadowed passwords (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Local accounts can uses shadowed passwords. With shadowed passwords, The passwords are saved in shadow password file, /etc/shadow, encrypted by a salted one-way hash. Accounts with a shadowed password have an x in the second field in /etc/passwd. Rationale: The /etc/passwd file also contains information like user ID's and group ID's that are used by many system programs. Therefore, the /etc/passwd file must remain world readable. In spite of encoding the password with a randomly-generated one-way hash function, an attacker could still break the system if they got access to the /etc/passwd file. This can be mitigated by using shadowed passwords, thus moving the passwords in the /etc/passwd file to /etc/shadow. The /etc/shadow file is set so only root will be able to read and write. This helps mitigate the risk of an attacker gaining access to the encoded passwords with which to perform a dictionary attack. Note: • All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user. • A user account with an empty second field in /etc/passwd allows the account to be logged into by providing only the username. Audit: Run the following command and verify that no output is returned: # awk -F: '($2 != "x" ) { print "User: \"" $1 "\" is not set to shadowed passwords "}' /etc/passwd Remediation: Run the following command to set accounts to use shadowed passwords and migrate passwords in /etc/passwd to /etc/shadow: # pwconv Investigate to determine if the account is logged in and what it is being used for, to determine if it needs to be forced off. Page 884 Internal Only - General References: 1. NIST SP 800-53 Rev. 5: IA-5 2. PWCONV(8) Additional Information: The pwconv command creates shadow from passwd and an optionally existing shadow. • The pwunconv command creates passwd from passwd and shadow and then removes shadow. • The grpconv command creates gshadow from group and an optionally existing gshadow. • The grpunconv command creates group from group and gshadow and then removes gshadow. These four programs all operate on the normal and shadow password and group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow. Each program acquires the necessary locks before conversion. pwconv and grpconv are similar. First, entries in the shadowed file which don't exist in the main file are removed. Then, shadowed entries which don't have x' as the password in the main file are updated. Any missing shadowed entries are added. Finally, passwords in the main file are replaced with x'. These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand. pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and PASS_WARN_AGE from /etc/login.defs when adding new entries to /etc/shadow. pwunconv and grpunconv are similar. Passwords in the main file are updated from the shadowed file. Entries which exist in the main file but not in the shadowed file are left alone. Finally, the shadowed file is removed. Some password aging information is lost by pwunconv. It will convert what it can. CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.11 Encrypt Sensitive Data at Rest Encrypt sensitive data at rest on servers, applications, and databases containing sensitive data. Storage-layer encryption, also known as server-side encryption, v8 meets the minimum requirement of this Safeguard. Additional encryption methods ● ● may include application-layer encryption, also known as client-side encryption, where access to the data storage device(s) does not permit access to the plain-text data. v7 16.4 Encrypt or Hash all Authentication Credentials ● ● Encrypt or hash with a salt all authentication credentials when stored. Page 885 Internal Only - General 7.2.2 Ensure /etc/shadow password fields are not empty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: An account with an empty password field means that anybody may log in as that user without providing a password. Rationale: All accounts must have passwords or be locked to prevent the account from being used by an unauthorized user. Audit: Run the following command and verify that no output is returned: # awk -F: '($2 == "" ) { print $1 " does not have a password "}' /etc/shadow Remediation: If any accounts in the /etc/shadow file do not have a password, run the following command to lock the account until it can be determined why it does not have a password: # passwd -l Also, check to see if the account is logged in and investigate what it is being used for to determine if it needs to be forced off. References: 1. NIST SP 800-53 Rev. 5: IA-5 2. NIST SP 800-53 Revision 5 :: CM-6 b 3. NIST SP 800-53A :: CM-6.1 (iv) Page 886 Internal Only - General Additional Information: Red Hat Enterprise Linux 8 Security Technical Implementation Guide Version 1, Release: 14 Benchmark Date: 24 APR 2024 Vul ID: V-251706 Rule ID: SV-251706r809342 STIG ID: RHEL-08-010121 Severity: CAT II CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 5.2 Use Unique Passwords v8 Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a ● ● ● 14-character password for accounts not using MFA. 4.4 Use Unique Passwords v7 Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that ● ● system. Page 887 Internal Only - General 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Over time, system administration errors and changes can lead to groups being defined in /etc/passwd but not in /etc/group . Rationale: Groups defined in the /etc/passwd file but not in the /etc/group file pose a threat to system security since group permissions are not properly managed. Audit: Run the following script to verify all GIDs in /etc/passwd exist in /etc/group: #!/usr/bin/env bash { a_passwd_group_gid=("$(awk -F: '{print $4}' /etc/passwd | sort -u)") a_group_gid=("$(awk -F: '{print $3}' /etc/group | sort -u)") a_passwd_group_diff=("$(printf '%s\n' "${a_group_gid[@]}" "${a_passwd_group_gid[@]}" | sort | uniq -u)") while IFS= read -r l_gid; do awk -F: '($4 == '"$l_gid"') {print " - User: \"" $1 "\" has GID: \"" $4 "\" which does not exist in /etc/group" }' /etc/passwd done < <(printf '%s\n' "${a_passwd_group_gid[@]}" "${a_passwd_group_diff[@]}" | sort | uniq -D | uniq) unset a_passwd_group_gid; unset a_group_gid; unset a_passwd_group_diff } Nothing should be returned Remediation: Analyze the output of the Audit step above and perform the appropriate action to correct any discrepancies found. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 888 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote ● ● ● file systems, databases, and applications. 14.6 Train Workforce Members on Recognizing and v8 Reporting Security Incidents ● ● ● Train workforce members to be able to recognize a potential incident and be able to report such an incident. Page 889 Internal Only - General 7.2.4 Ensure shadow group is empty (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The shadow group allows system programs which require access the ability to read the /etc/shadow file. No users should be assigned to the shadow group. Rationale: Any users assigned to the shadow group would be granted read access to the /etc/shadow file. If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed passwords to break them. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert additional user accounts. Audit: Run the following commands and verify no results are returned: # awk -F: '($1=="shadow") {print $NF}' /etc/group # awk -F: '($4 == '"$(getent group shadow | awk -F: '{print $3}' | xargs)"') {print " - user: \"" $1 "\" primary group is the shadow group"}' /etc/passwd Remediation: Run the following command to remove all users from the shadow group # sed -ri 's/(^shadow:[^:]*:[^:]*:)([^:]+$)/\1/' /etc/group Change the primary group of any users with shadow as their primary group. # usermod -g References: 1. NIST SP 800-53 Rev. 5: IA-5 Page 890 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 891 Internal Only - General 7.2.5 Ensure no duplicate UIDs exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the useradd program will not let you create a duplicate User ID (UID), it is possible for an administrator to manually edit the /etc/passwd file and change the UID field. Rationale: Users must be assigned unique UIDs for accountability and to ensure appropriate access protections. Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062, SRG-OS- 000042-GPOS-00020 Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_uid; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate UID: \"$l_uid\" Users: \"$(awk -F: '($3 == n) { print $1 }' n=$l_uid /etc/passwd | xargs)\"" fi done < <(cut -f3 -d":" /etc/passwd | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique UIDs and review all files owned by the shared UIDs to determine which UID they are supposed to belong to. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 2. NIST SP 800-53A :: IA-2.1 Page 892 Internal Only - General Additional Information: Red Hat Enterprise Linux 8 Security Technical Implementation Guide Version 1, Release: 14 Benchmark Date: 24 APR 2024 Vul ID: V-230371 Rule ID: SV-230371r627750 STIG ID: RHEL-08-020240 Severity: CAT II CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 893 Internal Only - General 7.2.6 Ensure no duplicate GIDs exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the groupadd program will not let you create a duplicate Group ID (GID), it is possible for an administrator to manually edit the /etc/group file and change the GID field. Rationale: User groups must be assigned unique GIDs for accountability and to ensure appropriate access protections. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_gid; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate GID: \"$l_gid\" Groups: \"$(awk -F: '($3 == n) { print $1 }' n=$l_gid /etc/group | xargs)\"" fi done < <(cut -f3 -d":" /etc/group | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique GIDs and review all files owned by the shared GID to determine which group they are supposed to belong to. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Additional Information: You can also use the grpck command to check for other inconsistencies in the /etc/group file. Page 894 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 895 Internal Only - General 7.2.7 Ensure no duplicate user names exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the useradd program will not let you create a duplicate user name, it is possible for an administrator to manually edit the /etc/passwd file and change the user name. Rationale: If a user is assigned a duplicate user name, it will create and have access to files with the first UID for that username in /etc/passwd . For example, if "test4" has a UID of 1000 and a subsequent "test4" entry has a UID of 2000, logging in as "test4" will use UID 1000. Effectively, the UID is shared, which is a security problem. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_user; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate User: \"$l_user\" Users: \"$(awk -F: '($1 == n) { print $1 }' n=$l_user /etc/passwd | xargs)\"" fi done < <(cut -f1 -d":" /etc/passwd | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique user names for the users. File ownerships will automatically reflect the change as long as the users have unique UIDs. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 896 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 897 Internal Only - General 7.2.8 Ensure no duplicate group names exist (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: Although the groupadd program will not let you create a duplicate group name, it is possible for an administrator to manually edit the /etc/group file and change the group name. Rationale: If a group is assigned a duplicate group name, it will create and have access to files with the first GID for that group in /etc/group . Effectively, the GID is shared, which is a security problem. Audit: Run the following script and verify no results are returned: #!/usr/bin/env bash { while read -r l_count l_group; do if [ "$l_count" -gt 1 ]; then echo -e "Duplicate Group: \"$l_group\" Groups: \"$(awk -F: '($1 == n) { print $1 }' n=$l_group /etc/group | xargs)\"" fi done < <(cut -f1 -d":" /etc/group | sort -n | uniq -c) } Remediation: Based on the results of the audit script, establish unique names for the user groups. File group ownerships will automatically reflect the change as long as the groups have unique GIDs. References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 898 Internal Only - General CIS Controls: Controls Version Control IG 1 IG 2 IG 3 v8 0.0 Explicitly Not Mapped Explicitly Not Mapped v7 0.0 Explicitly Not Mapped Explicitly Not Mapped Page 899 Internal Only - General 7.2.9 Ensure local interactive user home directories are configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: The user home directory is space defined for the particular user to set local environment variables and to store personal files. While the system administrator can establish secure permissions for users' home directories, the users can easily override these. Users can be defined in /etc/passwd without a home directory or with a home directory that does not actually exist. Rationale: Since the user is accountable for files stored in the user home directory, the user must be the owner of the directory. Group or world-writable user home directories may enable malicious users to steal or modify other users' data or to gain another user's system privileges. If the user's home directory does not exist or is unassigned, the user will be placed in "/" and will not be able to write any files or have local environment variables set. Audit: Run the following script to Ensure: • local interactive user home directories exist • Ensure local interactive users own their home directories • Ensure local interactive user home directories are mode 750 or more restrictive Page 900 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_exists2=() a_mode2=() a_owner2=() l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" l_mask='0027'; l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" l_users="$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd | wc -l)" [ "$l_users" -gt 10000 ] && printf '%s\n' "" " ** INFO **" \ " $l_users Local interactive users found on the system" " This may be a long running check" " **********" while IFS=" " read -r l_user l_home; do if [ -d "$l_home" ]; then while IFS=: read -r l_own l_mode; do [ "$l_user" != "$l_own" ] && a_owner2+=(" - User: \"$l_user\" Home \"$l_home\" is owned by: \"$l_own\"") [ $(( $l_mode & $l_mask )) -gt 0 ] && a_mode2+=(" - User: \"$l_user\" Home \"$l_home\" is mode: \"$l_mode\"" \ " should be mode: \"$l_max\" or more restrictive") done <<< "$(stat -Lc '%U:%#a' "$l_home")" else a_exists2+=(" - User: \"$l_user\" Home Directory: \"$l_home\" Doesn't exist") fi done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" [ "${#a_exists2[@]}" -gt 0 ] && a_output2+=("${a_exists2[@]}") || \ a_output+=(" - All interactive users home directories exist") [ "${#a_mode2[@]}" -gt 0 ] && a_output2+=("${a_mode2[@]}") || \ a_output+=(" - All interactive users home directories are mode \"$l_max\" or more restrictive") [ "${#a_owner2[@]}" -gt 0 ] && a_output2+=("${a_owner2[@]}") || \ a_output+=(" - All interactive users own their home directory") if [ "${#a_output2[@]}" -le 0 ]; then printf '%s\n' "" "- Audit Result:" " ** PASS **" "${a_output[@]}" else printf '%s\n' "" "- Audit Result:" " ** FAIL **" " - Reason(s) for audit failure:" "${a_output2[@]}" [ "${#a_output[@]}" -gt 0 ] && printf '%s\n' "- Correctly set:" "${a_output[@]}" fi } Page 901 Internal Only - General Remediation: If a local interactive users' home directory is undefined and/or doesn't exist, follow local site policy and perform one of the following: • Lock the user account • Remove the user from the system • create a directory for the user. If undefined, edit /etc/passwd and add the absolute path to the directory to the last field of the user. Run the following script to: • Remove excessive permissions from local interactive users home directories • Update the home directory's owner Page 902 Internal Only - General #!/usr/bin/env bash { a_output=() a_output2=() a_exists2=() a_mode2=() a_owner2=() l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" l_mask='0027'; l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" l_users="$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd | wc -l)" [ "$l_users" -gt 10000 ] && printf '%s\n' "" " ** INFO **" \ " $l_users Local interactive users found on the system" " This may be a long running process" " **********" while IFS=" " read -r l_user l_home; do if [ -d "$l_home" ]; then while IFS=: read -r l_own l_mode; do if [ "$l_user" != "$l_own" ]; then a_owner2+=(" - User: \"$l_user\" Home \"$l_home\" is owned by: \"$l_own\"" \ " changing owner to: \"$l_user\"") && chown "$l_user" "$l_home" fi if [ $(( $l_mode & $l_mask )) -gt 0 ]; then a_mode2+=(" - User: \"$l_user\" Home \"$l_home\" is mode: \"$l_mode\"" \ " changing to mode: \"$l_max\" or more restrictive") chmod g-w,o-rwx "$l_home" fi done <<< "$(stat -Lc '%U:%#a' "$l_home")" else a_exists2+=(" - User: \"$l_user\" Home Directory: \"$l_home\" Doesn't exist") fi done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" [ "${#a_exists2[@]}" -gt 0 ] && a_output2+=("${a_exists2[@]}") [ "${#a_mode2[@]}" -gt 0 ] && a_output2+=("${a_mode2[@]}") [ "${#a_owner2[@]}" -gt 0 ] && a_output2+=("${a_owner2[@]}") if [ "${#a_output2[@]}" -gt 0 ]; then printf '%s\n' "" "${a_output2[@]}" else printf '%s\n' "" "- No changes required" fi } References: 1. NIST SP 800-53 Revision 5 :: CM-6 b 2. NIST SP 800-53A :: CM-6.1 (iv) Page 903 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 904 Internal Only - General 7.2.10 Ensure local interactive user dot files access is configured (Automated) Profile Applicability: • Level 1 - Server • Level 1 - Workstation Description: While the system administrator can establish secure permissions for users' "dot" files, the users can easily override these. • .forward file specifies an email address to forward the user's mail to. • .rhost file provides the "remote authentication" database for the rcp, rlogin, and rsh commands and the rcmd() function. These files bypass the standard password-based user authentication mechanism. They specify remote hosts and users that are considered trusted (i.e. are allowed to access the local system without supplying a password) • .netrc file contains data for logging into a remote host or passing authentication to an API. • .bash_history file keeps track of the user’s commands. Rationale: User configuration files with excessive or incorrect access may enable malicious users to steal or modify other users' data or to gain another user's system privileges. Audit: Run the following script to verify local interactive user dot files: • Don't include .forward, .rhost, or .netrc files • Are mode 0644 or more restrictive • Are owned by the local interactive user • Are group owned by the user's primary group • .bash_history is mode 0600 or more restrictive Note: If a .netrc file is required, and follows local site policy, it should be mode 0600 or more restrictive. Page 905 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=() l_maxsize="1000" # Maximum number of local interactive users before warning (Default 1,000) l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" a_user_and_home=() # Create array with local users and their home directories while read -r l_local_user l_local_user_home; do # Populate array with users and user home location [[ -n "$l_local_user" && -n "$l_local_user_home" ]] && a_user_and_home+=("$l_local_user:$l_local_user_home") done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" l_asize="${#a_user_and_home[@]}" # Here if we want to look at number of users before proceeding [ "${#a_user_and_home[@]}" -gt "$l_maxsize" ] && printf '%s\n' "" " ** INFO **" \ " - \"$l_asize\" Local interactive users found on the system" \ " - This may be a long running check" "" file_access_chk() { a_access_out=() l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" if [ $(( $l_mode & $l_mask )) -gt 0 ]; then a_access_out+=(" - File: \"$l_hdfile\" is mode: \"$l_mode\" and should be mode: \"$l_max\" or more restrictive") fi if [[ ! "$l_owner" =~ ($l_user) ]]; then a_access_out+=(" - File: \"$l_hdfile\" owned by: \"$l_owner\" and should be owned by \"${l_user//|/ or }\"") fi if [[ ! "$l_gowner" =~ ($l_group) ]]; then a_access_out+=(" - File: \"$l_hdfile\" group owned by: \"$l_gowner\" and should be group owned by \"${l_group//|/ or }\"") fi } while IFS=: read -r l_user l_home; do a_dot_file=(); a_netrc=(); a_netrc_warn=(); a_bhout=(); a_hdirout=() if [ -d "$l_home" ]; then l_group="$(id -gn "$l_user" | xargs)";l_group="${l_group// /|}" while IFS= read -r -d $'\0' l_hdfile; do while read -r l_mode l_owner l_gowner; do case "$(basename "$l_hdfile")" in .forward | .rhost ) a_dot_file+=(" - File: \"$l_hdfile\" exists") ;; .netrc ) l_mask='0177'; file_access_chk if [ "${#a_access_out[@]}" -gt 0 ]; then a_netrc+=("${a_access_out[@]}") else a_netrc_warn+=(" - File: \"$l_hdfile\" exists") fi ;; .bash_history ) l_mask='0177'; file_access_chk [ "${#a_access_out[@]}" -gt 0 ] && a_bhout+=("${a_access_out[@]}") ;; * ) l_mask='0133'; file_access_chk [ "${#a_access_out[@]}" -gt 0 ] && a_hdirout+=("${a_access_out[@]}") ;; esac done < <(stat -Lc '%#a %U %G' "$l_hdfile") done < <(find "$l_home" -xdev -type f -name '.*' -print0) fi if [[ "${#a_dot_file[@]}" -gt 0 || "${#a_netrc[@]}" -gt 0 || "${#a_bhout[@]}" -gt 0 || "${#a_hdirout[@]}" -gt 0 ]]; then a_output2+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_dot_file[@]}" "${a_netrc[@]}" "${a_bhout[@]}" "${a_hdirout[@]}") fi [ "${#a_netrc_warn[@]}" -gt 0 ] && a_output3+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_netrc_warn[@]}") done <<< "$(printf '%s\n' "${a_user_and_home[@]}")" if [ "${#a_output2[@]}" -le 0 ]; then # If l_output2 is empty, we pass [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' " ** WARNING **" "${a_output3[@]}" printf '%s\n' "- Audit Result:" " ** PASS **" else printf '%s\n' "- Audit Result:" " ** FAIL **" " - * Reasons for audit failure * :" "${a_output2[@]}" "" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' " ** WARNING **" "${a_output3[@]}" fi } Page 906 Internal Only - General Remediation: Making global modifications to users' files without alerting the user community can result in unexpected outages and unhappy users. Therefore, it is recommended that a monitoring policy be established to report user dot file permissions and determine the action to be taken in accordance with site policy. The following script will: • remove excessive permissions on dot files within interactive users' home directories • change ownership of dot files within interactive users' home directories to the user • change group ownership of dot files within interactive users' home directories to the user's primary group • list .forward and .rhost files to be investigated and manually deleted Page 907 Internal Only - General #!/usr/bin/env bash { a_output2=(); a_output3=() l_maxsize="1000" # Maximum number of local interactive users before warning (Default 1,000) l_valid_shells="^($( awk -F\/ '$NF != "nologin" {print}' /etc/shells | sed -rn '/^\//{s,/,\\\\/,g;p}' | paste -s -d '|' - ))$" a_user_and_home=() # Create array with local users and their home directories while read -r l_local_user l_local_user_home; do # Populate array with users and user home location [[ -n "$l_local_user" && -n "$l_local_user_home" ]] && a_user_and_home+=("$l_local_user:$l_local_user_home") done <<< "$(awk -v pat="$l_valid_shells" -F: '$(NF) ~ pat { print $1 " " $(NF-1) }' /etc/passwd)" l_asize="${#a_user_and_home[@]}" # Here if we want to look at number of users before proceeding [ "${#a_user_and_home[@]}" -gt "$l_maxsize" ] && printf '%s\n' "" " ** INFO **" \ " - \"$l_asize\" Local interactive users found on the system" \ " - This may be a long running check" "" file_access_fix() { a_access_out=() l_max="$( printf '%o' $(( 0777 & ~$l_mask)) )" if [ $(( $l_mode & $l_mask )) -gt 0 ]; then printf '%s\n' "" " - File: \"$l_hdfile\" is mode: \"$l_mode\" and should be mode: \"$l_max\" or more restrictive" \ " Updating file: \"$l_hdfile\" to be mode: \"$l_max\" or more restrictive" chmod "$l_change" "$l_hdfile" fi if [[ ! "$l_owner" =~ ($l_user) ]]; then printf '%s\n' "" " - File: \"$l_hdfile\" owned by: \"$l_owner\" and should be owned by \"${l_user//|/ or }\"" \ " Updating file: \"$l_hdfile\" to be owned by \"${l_user//|/ or }\"" chown "$l_user" "$l_hdfile" fi if [[ ! "$l_gowner" =~ ($l_group) ]]; then printf '%s\n' "" " - File: \"$l_hdfile\" group owned by: \"$l_gowner\" and should be group owned by \"${l_group//|/ or }\"" \ " Updating file: \"$l_hdfile\" to be group owned by \"${l_group//|/ or }\"" chgrp "$l_group" "$l_hdfile" fi } while IFS=: read -r l_user l_home; do a_dot_file=(); a_netrc=(); a_netrc_warn=(); a_bhout=(); a_hdirout=() if [ -d "$l_home" ]; then l_group="$(id -gn "$l_user" | xargs)";l_group="${l_group// /|}" while IFS= read -r -d $'\0' l_hdfile; do while read -r l_mode l_owner l_gowner; do case "$(basename "$l_hdfile")" in .forward | .rhost ) a_dot_file+=(" - File: \"$l_hdfile\" exists" " Please review and manually delete this file") ;; .netrc ) l_mask='0177'; l_change="u-x,go-rwx"; file_access_fix a_netrc_warn+=(" - File: \"$l_hdfile\" exists") ;; .bash_history ) l_mask='0177'; l_change="u-x,go-rwx"; file_access_fix ;; * ) l_mask='0133'; l_change="u-x,go-wx"; file_access_fix ;; esac done < <(stat -Lc '%#a %U %G' "$l_hdfile") done < <(find "$l_home" -xdev -type f -name '.*' -print0) fi [ "${#a_dot_file[@]}" -gt 0 ] && a_output2+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_dot_file[@]}") [ "${#a_netrc_warn[@]}" -gt 0 ] && a_output3+=(" - User: \"$l_user\" Home Directory: \"$l_home\"" "${a_netrc_warn[@]}") done <<< "$(printf '%s\n' "${a_user_and_home[@]}")" [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " ** WARNING **" "${a_output3[@]}" "" [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" } References: 1. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5 Page 908 Internal Only - General CIS Controls: Controls Control IG 1 IG 2 IG 3 Version 3.3 Configure Data Access Control Lists v8 Configure data access control lists based on a user’s need to know. Apply data access control lists, also known as access permissions, to local and remote file ● ● ● systems, databases, and applications. 14.6 Protect Information through Access Control Lists Protect all information stored on systems with file system, network share, v7 claims, application, or database specific access control lists. These controls will enforce the principle that only authorized individuals should have access to the ● ● ● information based on their need to access the information as a part of their responsibilities. Page 909 Internal Only - General Appendix: Summary Table CIS Benchmark Recommendation Set Correctly Yes No 1 Initial Setup 1.1 Filesystem 1.1.1 Configure Filesystem Kernel Modules 1.1.1.1 Ensure cramfs kernel module is not available   (Automated) 1.1.1.2 Ensure freevxfs kernel module is not available   (Automated) 1.1.1.3 Ensure hfs kernel module is not available (Automated)   1.1.1.4 Ensure hfsplus kernel module is not available   (Automated) 1.1.1.5 Ensure jffs2 kernel module is not available (Automated)   1.1.1.6 Ensure overlay kernel module is not available   (Automated) 1.1.1.7 Ensure squashfs kernel module is not available   (Automated) 1.1.1.8 Ensure udf kernel module is not available (Automated)   1.1.1.9 Ensure usb-storage kernel module is not available   (Automated) 1.1.1.10 Ensure unused filesystems kernel modules are not   available (Manual) 1.1.1.11 Ensure firewire-core kernel module is not available   (Automated) 1.1.2 Configure Filesystem Partitions 1.1.2.1 Configure /tmp 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition (Automated)   1.1.2.1.2 Ensure nodev option set on /tmp partition (Automated)   1.1.2.1.3 Ensure nosuid option set on /tmp partition (Automated)   1.1.2.1.4 Ensure noexec option set on /tmp partition (Automated)   1.1.2.2 Configure /dev/shm 1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   (Automated) Page 910 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.1.2.2.2 Ensure nodev option set on /dev/shm partition   (Automated) 1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   (Automated) 1.1.2.2.4 Ensure noexec option set on /dev/shm partition   (Automated) 1.1.2.3 Configure /home 1.1.2.3.1 Ensure separate partition exists for /home (Automated)   1.1.2.3.2 Ensure nodev option set on /home partition (Automated)   1.1.2.3.3 Ensure nosuid option set on /home partition (Automated)   1.1.2.4 Configure /var 1.1.2.4.1 Ensure separate partition exists for /var (Automated)   1.1.2.4.2 Ensure nodev option set on /var partition (Automated)   1.1.2.4.3 Ensure nosuid option set on /var partition (Automated)   1.1.2.5 Configure /var/tmp 1.1.2.5.1 Ensure separate partition exists for /var/tmp (Automated)   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   (Automated) 1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   (Automated) 1.1.2.5.4 Ensure noexec option set on /var/tmp partition   (Automated) 1.1.2.6 Configure /var/log 1.1.2.6.1 Ensure separate partition exists for /var/log (Automated)   1.1.2.6.2 Ensure nodev option set on /var/log partition   (Automated) 1.1.2.6.3 Ensure nosuid option set on /var/log partition   (Automated) 1.1.2.6.4 Ensure noexec option set on /var/log partition   (Automated) 1.1.2.7 Configure /var/log/audit 1.1.2.7.1 Ensure separate partition exists for /var/log/audit   (Automated) 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   (Automated) Page 911 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   (Automated) 1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   (Automated) 1.2 Package Management 1.2.1 Configure Package Repositories 1.2.1.1 Ensure GPG keys are configured (Manual)   1.2.1.2 Ensure package manager repositories are configured   (Manual) 1.2.2 Configure Package Updates 1.2.2.1 Ensure updates, patches, and additional security   software are installed (Manual) 1.3 Mandatory Access Control 1.3.1 Configure AppArmor 1.3.1.1 Ensure the apparmor packages are installed   (Automated) 1.3.1.2 Ensure AppArmor is enabled (Automated)   1.3.1.3 Ensure all AppArmor Profiles are not disabled   (Automated) 1.3.1.4 Ensure all AppArmor Profiles are enforcing (Automated)   1.4 Configure Bootloader 1.4.1 Ensure bootloader password is set (Automated)   1.4.2 Ensure access to bootloader config is configured   (Automated) 1.5 Configure Additional Process Hardening 1.5.1 Ensure randomize_va_space is configured (Automated)   1.5.2 Ensure ptrace_scope is configured (Automated)   1.5.3 Ensure suid_dumpable is configured (Automated)   1.5.4 Ensure core file size is configured (Automated)   1.5.5 Ensure prelink is not installed (Automated)   1.5.6 Ensure Automatic Error Reporting is configured   (Automated) 1.6 Configure Command Line Warning Banners 1.6.1 Ensure /etc/motd is configured (Automated)   Page 912 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 1.6.2 Ensure /etc/issue is configured (Automated)   1.6.3 Ensure /etc/issue.net is configured (Automated)   1.6.4 Ensure access to /etc/motd is configured (Automated)   1.6.5 Ensure access to /etc/issue is configured (Automated)   1.6.6 Ensure access to /etc/issue.net is configured   (Automated) 1.7 Configure GNOME Display Manager 1.7.1 Ensure GDM is removed (Automated)   1.7.2 Ensure GDM login banner is configured (Automated)   1.7.3 Ensure GDM disable-user-list option is enabled   (Automated) 1.7.4 Ensure GDM screen locks when the user is idle   (Automated) 1.7.5 Ensure GDM screen locks cannot be overridden   (Automated) 1.7.6 Ensure GDM automatic mounting of removable media is   disabled (Automated) 1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden (Automated) 1.7.8 Ensure GDM autorun-never is enabled (Automated)   1.7.9 Ensure GDM autorun-never is not overridden   (Automated) 1.7.10 Ensure XDMCP is not enabled (Automated)   1.7.11 Ensure Xwayland is configured (Automated)   2 Services 2.1 Configure Server Services 2.1.1 Ensure autofs services are not in use (Automated)   2.1.2 Ensure avahi daemon services are not in use   (Automated) 2.1.3 Ensure dhcp server services are not in use (Automated)   2.1.4 Ensure dns server services are not in use (Automated)   2.1.5 Ensure dnsmasq services are not in use (Automated)   2.1.6 Ensure ftp server services are not in use (Automated)   2.1.7 Ensure ldap server services are not in use (Automated)   Page 913 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 2.1.8 Ensure message access server services are not in use   (Automated) 2.1.9 Ensure network file system services are not in use   (Automated) 2.1.10 Ensure nis server services are not in use (Automated)   2.1.11 Ensure print server services are not in use (Automated)   2.1.12 Ensure rpcbind services are not in use (Automated)   2.1.13 Ensure rsync services are not in use (Automated)   2.1.14 Ensure samba file server services are not in use   (Automated) 2.1.15 Ensure snmp services are not in use (Automated)   2.1.16 Ensure tftp server services are not in use (Automated)   2.1.17 Ensure web proxy server services are not in use   (Automated) 2.1.18 Ensure web server services are not in use (Automated)   2.1.19 Ensure xinetd services are not in use (Automated)   2.1.20 Ensure X window server services are not in use   (Automated) 2.1.21 Ensure mail transfer agents are configured for local-only   mode (Automated) 2.1.22 Ensure only approved services are listening on a   network interface (Manual) 2.2 Configure Client Services 2.2.1 Ensure nis client is not installed (Automated)   2.2.2 Ensure rsh client is not installed (Automated)   2.2.3 Ensure talk client is not installed (Automated)   2.2.4 Ensure telnet client is not installed (Automated)   2.2.5 Ensure ldap client is not installed (Automated)   2.2.6 Ensure ftp client is not installed (Automated)   2.3 Configure Time Synchronization 2.3.1 Ensure time synchronization is in use 2.3.1.1 Ensure a single time synchronization daemon is in use   (Automated) 2.3.2 Configure systemd-timesyncd Page 914 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver (Automated) 2.3.2.2 Ensure systemd-timesyncd is enabled and running   (Automated) 2.3.3 Configure chrony 2.3.3.1 Ensure chrony is configured with authorized timeserver   (Automated) 2.3.3.2 Ensure chrony is running as user _chrony (Automated)   2.3.3.3 Ensure chrony is enabled and running (Automated)   2.4 Job Schedulers 2.4.1 Configure cron 2.4.1.1 Ensure cron daemon is enabled and active (Automated)   2.4.1.2 Ensure access to /etc/crontab is configured (Automated)   2.4.1.3 Ensure access to /etc/cron.hourly is configured   (Automated) 2.4.1.4 Ensure access to /etc/cron.daily is configured   (Automated) 2.4.1.5 Ensure access to /etc/cron.weekly is configured   (Automated) 2.4.1.6 Ensure access to /etc/cron.monthly is configured   (Automated) 2.4.1.7 Ensure access to /etc/cron.yearly is configured   (Automated) 2.4.1.8 Ensure access to /etc/cron.d is configured (Automated)   2.4.1.9 Ensure access to crontab is configured (Automated)   2.4.2 Configure at 2.4.2.1 Ensure access to at is configured (Automated)   3 Network 3.1 Configure Network Devices 3.1.1 Ensure IPv6 status is identified (Manual)   3.1.2 Ensure wireless interfaces are not available (Automated)   3.1.3 Ensure bluetooth services are not in use (Automated)   3.2 Configure Network Kernel Modules 3.2.1 Ensure dccp kernel module is not available (Automated)   Page 915 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 3.2.2 Ensure tipc kernel module is not available (Automated)   3.2.3 Ensure rds kernel module is not available (Automated)   3.2.4 Ensure sctp kernel module is not available (Automated)   3.3 Configure Network Kernel Parameters 3.3.1 Configure IPv4 parameters 3.3.1.1 Ensure net.ipv4.ip_forward is configured (Automated)   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   (Automated) 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   (Automated) 3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   (Automated) 3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   (Automated) 3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured (Automated) 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured (Automated) 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   (Automated) 3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured (Automated) 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   (Automated) 3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured (Automated) 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   (Automated) 3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   (Automated) 3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured (Automated) 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured (Automated) 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   (Automated) Page 916 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   (Automated) 3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   (Automated) 3.3.2 Configure IPv6 parameters 3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   (Automated) 3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   (Automated) 3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   (Automated) 3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured (Automated) 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured (Automated) 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured (Automated) 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   (Automated) 3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   (Automated) 4 Host Based Firewall 4.1 Configure Uncomplicated Firewall 4.1.1 Ensure ufw is installed (Automated)   4.1.2 Ensure ufw service is configured (Automated)   4.1.3 Ensure ufw incoming default is configured (Automated)   4.1.4 Ensure ufw outgoing default is configured (Automated)   4.1.5 Ensure ufw routed default is configured (Automated)   5 Access Control 5.1 Configure SSH Server 5.1.1 Ensure access to /etc/ssh/sshd_config is configured   (Automated) 5.1.2 Ensure access to SSH private host key files is   configured (Automated) Page 917 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.1.3 Ensure access to SSH public host key files is configured   (Automated) 5.1.4 Ensure sshd access is configured (Automated)   5.1.5 Ensure sshd Banner is configured (Automated)   5.1.6 Ensure sshd Ciphers are configured (Automated)   5.1.7 Ensure sshd ClientAliveInterval and   ClientAliveCountMax are configured (Automated) 5.1.8 Ensure sshd DisableForwarding is enabled (Automated)   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   (Automated) 5.1.10 Ensure sshd HostbasedAuthentication is disabled   (Automated) 5.1.11 Ensure sshd IgnoreRhosts is enabled (Automated)   5.1.12 Ensure sshd KexAlgorithms is configured (Automated)   5.1.13 Ensure sshd LoginGraceTime is configured (Automated)   5.1.14 Ensure sshd LogLevel is configured (Automated)   5.1.15 Ensure sshd MACs are configured (Automated)   5.1.16 Ensure sshd MaxAuthTries is configured (Automated)   5.1.17 Ensure sshd MaxSessions is configured (Automated)   5.1.18 Ensure sshd MaxStartups is configured (Automated)   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   (Automated) 5.1.20 Ensure sshd PermitRootLogin is disabled (Automated)   5.1.21 Ensure sshd PermitUserEnvironment is disabled   (Automated) 5.1.22 Ensure sshd UsePAM is enabled (Automated)   5.2 Configure privilege escalation 5.2.1 Ensure sudo is installed (Automated)   5.2.2 Ensure sudo commands use pty (Automated)   5.2.3 Ensure sudo log file exists (Automated)   5.2.4 Ensure users must provide password for escalation   (Automated) 5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally (Automated) Page 918 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.2.6 Ensure sudo timestamp_timeout is configured   (Automated) 5.2.7 Ensure access to the su command is restricted   (Automated) 5.3 Pluggable Authentication Modules 5.3.1 Configure PAM software packages 5.3.1.1 Ensure latest version of pam is installed (Automated)   5.3.1.2 Ensure latest version of libpam-modules is installed   (Automated) 5.3.1.3 Ensure latest version of libpam-pwquality is installed   (Automated) 5.3.2 Configure pam-auth-update profiles 5.3.2.1 Ensure pam_unix module is enabled (Automated)   5.3.2.2 Ensure pam_faillock module is enabled (Automated)   5.3.2.3 Ensure pam_pwquality module is enabled (Automated)   5.3.2.4 Ensure pam_pwhistory module is enabled (Automated)   5.3.3 Configure PAM Arguments 5.3.3.1 Configure pam_faillock module 5.3.3.1.1 Ensure password failed attempts lockout is configured   (Automated) 5.3.3.1.2 Ensure password unlock time is configured (Automated)   5.3.3.1.3 Ensure password failed attempts lockout includes root   account (Automated) 5.3.3.2 Configure pam_pwquality module 5.3.3.2.1 Ensure password number of changed characters is   configured (Automated) 5.3.3.2.2 Ensure minimum password length is configured   (Automated) 5.3.3.2.3 Ensure password complexity is configured (Manual)   5.3.3.2.4 Ensure password same consecutive characters is   configured (Automated) 5.3.3.2.5 Ensure password maximum sequential characters is   configured (Automated) 5.3.3.2.6 Ensure password dictionary check is enabled   (Automated) Page 919 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.3.3.2.7 Ensure password quality checking is enforced   (Automated) 5.3.3.2.8 Ensure password quality is enforced for the root user   (Automated) 5.3.3.3 Configure pam_pwhistory module 5.3.3.3.1 Ensure password history remember is configured   (Automated) 5.3.3.3.2 Ensure password history is enforced for the root user   (Automated) 5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   (Automated) 5.3.3.4 Configure pam_unix module 5.3.3.4.1 Ensure pam_unix does not include nullok (Automated)   5.3.3.4.2 Ensure pam_unix does not include remember   (Automated) 5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm (Automated) 5.3.3.4.4 Ensure pam_unix includes use_authtok (Automated)   5.4 User Accounts and Environment 5.4.1 Configure shadow password suite parameters 5.4.1.1 Ensure password expiration is configured (Automated)   5.4.1.2 Ensure minimum password days is configured (Manual)   5.4.1.3 Ensure password expiration warning days is configured   (Automated) 5.4.1.4 Ensure strong password hashing algorithm is configured   (Automated) 5.4.1.5 Ensure inactive password lock is configured (Automated)   5.4.1.6 Ensure all users last password change date is in the past   (Automated) 5.4.2 Configure root and system accounts and environment 5.4.2.1 Ensure root is the only UID 0 account (Automated)   5.4.2.2 Ensure root is the only GID 0 account (Automated)   5.4.2.3 Ensure group root is the only GID 0 group (Automated)   5.4.2.4 Ensure root account access is controlled (Automated)   5.4.2.5 Ensure root path integrity (Automated)   Page 920 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 5.4.2.6 Ensure root user umask is configured (Automated)   5.4.2.7 Ensure system accounts do not have a valid login shell   (Automated) 5.4.2.8 Ensure accounts without a valid login shell are locked   (Automated) 5.4.3 Configure user default environment 5.4.3.1 Ensure nologin is not listed in /etc/shells (Automated)   5.4.3.2 Ensure default user shell timeout is configured   (Automated) 5.4.3.3 Ensure default user umask is configured (Automated)   6 Logging and Auditing 6.1 System Logging 6.1.1 Configure journald 6.1.1.1 Configure systemd-journald service 6.1.1.1.1 Ensure journald service is active (Automated)   6.1.1.1.2 Ensure journald log file access is configured (Manual)   6.1.1.1.3 Ensure journald log file rotation is configured (Manual)   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   (Automated) 6.1.1.1.5 Ensure journald Storage is configured (Automated)   6.1.1.1.6 Ensure journald Compress is configured (Automated)   6.1.1.2 Configure systemd-journal-remote 6.1.1.2.1 Ensure systemd-journal-remote is installed (Automated)   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured (Manual) 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   (Automated) 6.1.1.2.4 Ensure systemd-journal-remote service is not in use   (Automated) 6.1.2 Configure rsyslog 6.1.2.1 Ensure rsyslog is installed (Automated)   6.1.2.2 Ensure rsyslog service is enabled and active   (Automated) Page 921 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.1.2.3 Ensure journald is configured to send logs to rsyslog   (Automated) 6.1.2.4 Ensure rsyslog log file creation mode is configured   (Automated) 6.1.2.5 Ensure rsyslog logging is configured (Manual)   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host (Manual) 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client (Automated) 6.1.2.8 Ensure logrotate is configured (Manual)   6.1.3 Configure Logfiles 6.1.3.1 Ensure access to all logfiles has been configured   (Automated) 6.2 System Auditing 6.2.1 Configure auditd Service 6.2.1.1 Ensure auditd packages are installed (Automated)   6.2.1.2 Ensure auditd service is enabled and active (Automated)   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled (Automated) 6.2.1.4 Ensure audit_backlog_limit is configured (Automated)   6.2.2 Configure Data Retention 6.2.2.1 Ensure audit log storage size is configured (Automated)   6.2.2.2 Ensure audit logs are not automatically deleted   (Automated) 6.2.2.3 Ensure system is disabled when audit logs are full   (Automated) 6.2.2.4 Ensure system warns when audit logs are low on space   (Automated) 6.2.3 Configure auditd Rules 6.2.3.1 Ensure changes to system administration scope   (sudoers) is collected (Automated) 6.2.3.2 Ensure actions as another user are always logged   (Automated) 6.2.3.3 Ensure events that modify the sudo log file are collected   (Automated) Page 922 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.2.3.4 Ensure events that modify date and time information are   collected (Automated) 6.2.3.5 Ensure events that modify the system's network   environment are collected (Automated) 6.2.3.6 Ensure use of privileged commands are collected   (Automated) 6.2.3.7 Ensure unsuccessful file access attempts are collected   (Automated) 6.2.3.8 Ensure events that modify user/group information are   collected (Automated) 6.2.3.9 Ensure discretionary access control permission   modification events are collected (Automated) 6.2.3.10 Ensure successful file system mounts are collected   (Automated) 6.2.3.11 Ensure session initiation information is collected   (Automated) 6.2.3.12 Ensure login and logout events are collected   (Automated) 6.2.3.13 Ensure file deletion events by users are collected   (Automated) 6.2.3.14 Ensure events that modify the system's Mandatory   Access Controls are collected (Automated) 6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected (Automated) 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected (Automated) 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected (Automated) 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected (Automated) 6.2.3.19 Ensure kernel module loading unloading and   modification is collected (Automated) 6.2.3.20 Ensure the audit configuration is immutable (Automated)   6.2.3.21 Ensure the running and on disk configuration is the same   (Manual) 6.2.4 Configure auditd File Access Page 923 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 6.2.4.1 Ensure audit log files mode is configured (Automated)   6.2.4.2 Ensure audit log files owner is configured (Automated)   6.2.4.3 Ensure audit log files group owner is configured   (Automated) 6.2.4.4 Ensure the audit log file directory mode is configured   (Automated) 6.2.4.5 Ensure audit configuration files mode is configured   (Automated) 6.2.4.6 Ensure audit configuration files owner is configured   (Automated) 6.2.4.7 Ensure audit configuration files group owner is   configured (Automated) 6.2.4.8 Ensure audit tools mode is configured (Automated)   6.2.4.9 Ensure audit tools owner is configured (Automated)   6.2.4.10 Ensure audit tools group owner is configured   (Automated) 6.3 Configure Filesystem Integrity Checking 6.3.1 Ensure AIDE is installed (Automated)   6.3.2 Ensure filesystem integrity is regularly checked   (Automated) 6.3.3 Ensure cryptographic mechanisms are used to protect   the integrity of audit tools (Automated) 7 System Maintenance 7.1 Configure system file and directory access 7.1.1 Ensure access to /etc/passwd is configured (Automated)   7.1.2 Ensure access to /etc/passwd- is configured   (Automated) 7.1.3 Ensure access to /etc/group is configured (Automated)   7.1.4 Ensure access to /etc/group- is configured (Automated)   7.1.5 Ensure access to /etc/shadow is configured (Automated)   7.1.6 Ensure access to /etc/shadow- is configured   (Automated) 7.1.7 Ensure access to /etc/gshadow is configured   (Automated) Page 924 Internal Only - General CIS Benchmark Recommendation Set Correctly Yes No 7.1.8 Ensure access to /etc/gshadow- is configured   (Automated) 7.1.9 Ensure access to /etc/shells is configured (Automated)   7.1.10 Ensure access to /etc/security/opasswd is configured   (Automated) 7.1.11 Ensure world writable files and directories are secured   (Automated) 7.1.12 Ensure no files or directories without an owner and a   group exist (Automated) 7.1.13 Ensure SUID and SGID files are reviewed (Manual)   7.2 Local User and Group Settings 7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords (Automated) 7.2.2 Ensure /etc/shadow password fields are not empty   (Automated) 7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   (Automated) 7.2.4 Ensure shadow group is empty (Automated)   7.2.5 Ensure no duplicate UIDs exist (Automated)   7.2.6 Ensure no duplicate GIDs exist (Automated)   7.2.7 Ensure no duplicate user names exist (Automated)   7.2.8 Ensure no duplicate group names exist (Automated)   7.2.9 Ensure local interactive user home directories are   configured (Automated) 7.2.10 Ensure local interactive user dot files access is   configured (Automated) Page 925 Internal Only - General Appendix: CIS Controls v7 IG 1 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.6.4 Ensure access to /etc/motd is configured   Page 926 Internal Only - General Recommendation Set Correctly Yes No 1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   2.1.1 Ensure autofs services are not in use   2.1.20 Ensure X window server services are not in use   2.2.1 Ensure nis client is not installed   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.14 Ensure sshd LogLevel is configured   5.1.20 Ensure sshd PermitRootLogin is disabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.2.1 Ensure pam_unix module is enabled   Page 927 Internal Only - General Recommendation Set Correctly Yes No 5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.6 Ensure use of privileged commands are collected   6.2.3.12 Ensure login and logout events are collected   6.2.3.13 Ensure file deletion events by users are collected   6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected Page 928 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.19 Ensure kernel module loading unloading and modification   is collected 6.2.3.20 Ensure the audit configuration is immutable   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 929 Internal Only - General Appendix: CIS Controls v7 IG 2 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure usb-storage kernel module is not available   1.1.1.10 Ensure unused filesystems kernel modules are not   available 1.1.1.11 Ensure firewire-core kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 930 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.1 Ensure randomize_va_space is configured   1.5.2 Ensure ptrace_scope is configured   1.5.6 Ensure Automatic Error Reporting is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   Page 931 Internal Only - General Recommendation Set Correctly Yes No 2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure tftp server services are not in use   2.1.17 Ensure web proxy server services are not in use   2.1.18 Ensure web server services are not in use   2.1.19 Ensure xinetd services are not in use   2.1.20 Ensure X window server services are not in use   2.1.21 Ensure mail transfer agents are configured for local-only   mode 2.1.22 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure dccp kernel module is not available   3.2.2 Ensure tipc kernel module is not available   3.2.3 Ensure rds kernel module is not available   3.2.4 Ensure sctp kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   Page 932 Internal Only - General Recommendation Set Correctly Yes No 3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   Page 933 Internal Only - General Recommendation Set Correctly Yes No 5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.14 Ensure sshd LogLevel is configured   5.1.15 Ensure sshd MACs are configured   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   5.1.20 Ensure sshd PermitRootLogin is disabled   5.1.22 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure minimum password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   Page 934 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host Page 935 Internal Only - General Recommendation Set Correctly Yes No 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure changes to system administration scope   (sudoers) is collected 6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify the system's network   environment are collected 6.2.3.6 Ensure use of privileged commands are collected   6.2.3.8 Ensure events that modify user/group information are   collected 6.2.3.9 Ensure discretionary access control permission   modification events are collected 6.2.3.10 Ensure successful file system mounts are collected   6.2.3.11 Ensure session initiation information is collected   6.2.3.12 Ensure login and logout events are collected   6.2.3.13 Ensure file deletion events by users are collected   6.2.3.14 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.19 Ensure kernel module loading unloading and modification   is collected Page 936 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.20 Ensure the audit configuration is immutable   6.2.3.21 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 937 Internal Only - General Appendix: CIS Controls v7 IG 3 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure usb-storage kernel module is not available   1.1.1.10 Ensure unused filesystems kernel modules are not   available 1.1.1.11 Ensure firewire-core kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 938 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.1 Ensure randomize_va_space is configured   1.5.2 Ensure ptrace_scope is configured   1.5.5 Ensure prelink is not installed   1.5.6 Ensure Automatic Error Reporting is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   Page 939 Internal Only - General Recommendation Set Correctly Yes No 2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure tftp server services are not in use   2.1.17 Ensure web proxy server services are not in use   2.1.18 Ensure web server services are not in use   2.1.19 Ensure xinetd services are not in use   2.1.20 Ensure X window server services are not in use   2.1.21 Ensure mail transfer agents are configured for local-only   mode 2.1.22 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.2 Ensure wireless interfaces are not available   3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure dccp kernel module is not available   3.2.2 Ensure tipc kernel module is not available   3.2.3 Ensure rds kernel module is not available   3.2.4 Ensure sctp kernel module is not available   Page 940 Internal Only - General Recommendation Set Correctly Yes No 3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   Page 941 Internal Only - General Recommendation Set Correctly Yes No 5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.14 Ensure sshd LogLevel is configured   5.1.15 Ensure sshd MACs are configured   5.1.16 Ensure sshd MaxAuthTries is configured   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   5.1.20 Ensure sshd PermitRootLogin is disabled   5.1.22 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure minimum password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   Page 942 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   Page 943 Internal Only - General Recommendation Set Correctly Yes No 6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure changes to system administration scope   (sudoers) is collected 6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify the system's network   environment are collected 6.2.3.6 Ensure use of privileged commands are collected   6.2.3.7 Ensure unsuccessful file access attempts are collected   6.2.3.8 Ensure events that modify user/group information are   collected 6.2.3.9 Ensure discretionary access control permission   modification events are collected 6.2.3.10 Ensure successful file system mounts are collected   6.2.3.11 Ensure session initiation information is collected   6.2.3.12 Ensure login and logout events are collected   6.2.3.13 Ensure file deletion events by users are collected   6.2.3.14 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected Page 944 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.19 Ensure kernel module loading unloading and modification   is collected 6.2.3.20 Ensure the audit configuration is immutable   6.2.3.21 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   6.3.1 Ensure AIDE is installed   6.3.2 Ensure filesystem integrity is regularly checked   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 945 Internal Only - General Page 946 Internal Only - General Appendix: CIS Controls v7 Unmapped Recommendations Recommendation Set Correctly Yes No 1.7.2 Ensure GDM login banner is configured   1.7.3 Ensure GDM disable-user-list option is enabled   1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden 2.4.1.7 Ensure access to /etc/cron.yearly is configured   6.2.2.3 Ensure system is disabled when audit logs are full   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   Page 947 Internal Only - General Appendix: CIS Controls v8 IG 1 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.9 Ensure usb-storage kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   Page 948 Internal Only - General Recommendation Set Correctly Yes No 1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   2.1.1 Ensure autofs services are not in use   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.14 Ensure sshd LogLevel is configured   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   5.1.20 Ensure sshd PermitRootLogin is disabled   5.1.22 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.4 Ensure users must provide password for escalation   Page 949 Internal Only - General Recommendation Set Correctly Yes No 5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure minimum password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   Page 950 Internal Only - General Recommendation Set Correctly Yes No 5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.8 Ensure logrotate is configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.20 Ensure the audit configuration is immutable   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   Page 951 Internal Only - General Recommendation Set Correctly Yes No 6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 952 Internal Only - General Appendix: CIS Controls v8 IG 2 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure usb-storage kernel module is not available   1.1.1.10 Ensure unused filesystems kernel modules are not   available 1.1.1.11 Ensure firewire-core kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 953 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.1 Ensure randomize_va_space is configured   1.5.2 Ensure ptrace_scope is configured   1.5.6 Ensure Automatic Error Reporting is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   2.1.12 Ensure rpcbind services are not in use   Page 954 Internal Only - General Recommendation Set Correctly Yes No 2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure tftp server services are not in use   2.1.17 Ensure web proxy server services are not in use   2.1.18 Ensure web server services are not in use   2.1.19 Ensure xinetd services are not in use   2.1.20 Ensure X window server services are not in use   2.1.21 Ensure mail transfer agents are configured for local-only   mode 2.1.22 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.2 Ensure wireless interfaces are not available   3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure dccp kernel module is not available   3.2.2 Ensure tipc kernel module is not available   3.2.3 Ensure rds kernel module is not available   3.2.4 Ensure sctp kernel module is not available   3.3.1.1 Ensure net.ipv4.ip_forward is configured   Page 955 Internal Only - General Recommendation Set Correctly Yes No 3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   5.1.2 Ensure access to SSH private host key files is configured   Page 956 Internal Only - General Recommendation Set Correctly Yes No 5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.14 Ensure sshd LogLevel is configured   5.1.15 Ensure sshd MACs are configured   5.1.16 Ensure sshd MaxAuthTries is configured   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   5.1.20 Ensure sshd PermitRootLogin is disabled   5.1.22 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure minimum password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   5.3.3.2.7 Ensure password quality checking is enforced   Page 957 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   6.1.2.5 Ensure rsyslog logging is configured   Page 958 Internal Only - General Recommendation Set Correctly Yes No 6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure changes to system administration scope   (sudoers) is collected 6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify the system's network   environment are collected 6.2.3.6 Ensure use of privileged commands are collected   6.2.3.7 Ensure unsuccessful file access attempts are collected   6.2.3.8 Ensure events that modify user/group information are   collected 6.2.3.9 Ensure discretionary access control permission   modification events are collected 6.2.3.10 Ensure successful file system mounts are collected   6.2.3.11 Ensure session initiation information is collected   6.2.3.12 Ensure login and logout events are collected   6.2.3.13 Ensure file deletion events by users are collected   6.2.3.14 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected Page 959 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.19 Ensure kernel module loading unloading and modification   is collected 6.2.3.20 Ensure the audit configuration is immutable   6.2.3.21 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   7.2.4 Ensure shadow group is empty   7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 960 Internal Only - General Appendix: CIS Controls v8 IG 3 Mapped Recommendations Recommendation Set Correctly Yes No 1.1.1.1 Ensure cramfs kernel module is not available   1.1.1.2 Ensure freevxfs kernel module is not available   1.1.1.3 Ensure hfs kernel module is not available   1.1.1.4 Ensure hfsplus kernel module is not available   1.1.1.5 Ensure jffs2 kernel module is not available   1.1.1.6 Ensure overlay kernel module is not available   1.1.1.7 Ensure squashfs kernel module is not available   1.1.1.8 Ensure udf kernel module is not available   1.1.1.9 Ensure usb-storage kernel module is not available   1.1.1.10 Ensure unused filesystems kernel modules are not   available 1.1.1.11 Ensure firewire-core kernel module is not available   1.1.2.1.1 Ensure /tmp is tmpfs or a separate partition   1.1.2.1.2 Ensure nodev option set on /tmp partition   1.1.2.1.3 Ensure nosuid option set on /tmp partition   1.1.2.1.4 Ensure noexec option set on /tmp partition   1.1.2.2.1 Ensure /dev/shm is tmpfs or a separate partition   1.1.2.2.2 Ensure nodev option set on /dev/shm partition   1.1.2.2.3 Ensure nosuid option set on /dev/shm partition   1.1.2.2.4 Ensure noexec option set on /dev/shm partition   1.1.2.3.1 Ensure separate partition exists for /home   1.1.2.3.2 Ensure nodev option set on /home partition   1.1.2.3.3 Ensure nosuid option set on /home partition   1.1.2.4.1 Ensure separate partition exists for /var   1.1.2.4.2 Ensure nodev option set on /var partition   1.1.2.4.3 Ensure nosuid option set on /var partition   1.1.2.5.1 Ensure separate partition exists for /var/tmp   1.1.2.5.2 Ensure nodev option set on /var/tmp partition   1.1.2.5.3 Ensure nosuid option set on /var/tmp partition   1.1.2.5.4 Ensure noexec option set on /var/tmp partition   1.1.2.6.1 Ensure separate partition exists for /var/log   1.1.2.6.2 Ensure nodev option set on /var/log partition   1.1.2.6.3 Ensure nosuid option set on /var/log partition   1.1.2.6.4 Ensure noexec option set on /var/log partition   1.1.2.7.1 Ensure separate partition exists for /var/log/audit   Page 961 Internal Only - General Recommendation Set Correctly Yes No 1.1.2.7.2 Ensure nodev option set on /var/log/audit partition   1.1.2.7.3 Ensure nosuid option set on /var/log/audit partition   1.1.2.7.4 Ensure noexec option set on /var/log/audit partition   1.2.1.1 Ensure GPG keys are configured   1.2.1.2 Ensure package manager repositories are configured   1.2.2.1 Ensure updates, patches, and additional security   software are installed 1.3.1.1 Ensure the apparmor packages are installed   1.3.1.2 Ensure AppArmor is enabled   1.3.1.3 Ensure all AppArmor Profiles are not disabled   1.3.1.4 Ensure all AppArmor Profiles are enforcing   1.4.1 Ensure bootloader password is set   1.4.2 Ensure access to bootloader config is configured   1.5.1 Ensure randomize_va_space is configured   1.5.2 Ensure ptrace_scope is configured   1.5.5 Ensure prelink is not installed   1.5.6 Ensure Automatic Error Reporting is configured   1.6.4 Ensure access to /etc/motd is configured   1.6.5 Ensure access to /etc/issue is configured   1.6.6 Ensure access to /etc/issue.net is configured   1.7.1 Ensure GDM is removed   1.7.4 Ensure GDM screen locks when the user is idle   1.7.5 Ensure GDM screen locks cannot be overridden   1.7.6 Ensure GDM automatic mounting of removable media is   disabled 1.7.8 Ensure GDM autorun-never is enabled   1.7.9 Ensure GDM autorun-never is not overridden   1.7.10 Ensure XDMCP is not enabled   1.7.11 Ensure Xwayland is configured   2.1.1 Ensure autofs services are not in use   2.1.2 Ensure avahi daemon services are not in use   2.1.3 Ensure dhcp server services are not in use   2.1.4 Ensure dns server services are not in use   2.1.5 Ensure dnsmasq services are not in use   2.1.6 Ensure ftp server services are not in use   2.1.7 Ensure ldap server services are not in use   2.1.8 Ensure message access server services are not in use   2.1.9 Ensure network file system services are not in use   2.1.10 Ensure nis server services are not in use   2.1.11 Ensure print server services are not in use   Page 962 Internal Only - General Recommendation Set Correctly Yes No 2.1.12 Ensure rpcbind services are not in use   2.1.13 Ensure rsync services are not in use   2.1.14 Ensure samba file server services are not in use   2.1.15 Ensure snmp services are not in use   2.1.16 Ensure tftp server services are not in use   2.1.17 Ensure web proxy server services are not in use   2.1.18 Ensure web server services are not in use   2.1.19 Ensure xinetd services are not in use   2.1.20 Ensure X window server services are not in use   2.1.21 Ensure mail transfer agents are configured for local-only   mode 2.1.22 Ensure only approved services are listening on a network   interface 2.2.1 Ensure nis client is not installed   2.2.2 Ensure rsh client is not installed   2.2.3 Ensure talk client is not installed   2.2.4 Ensure telnet client is not installed   2.2.5 Ensure ldap client is not installed   2.2.6 Ensure ftp client is not installed   2.3.1.1 Ensure a single time synchronization daemon is in use   2.3.2.1 Ensure systemd-timesyncd configured with authorized   timeserver 2.3.2.2 Ensure systemd-timesyncd is enabled and running   2.3.3.1 Ensure chrony is configured with authorized timeserver   2.3.3.3 Ensure chrony is enabled and running   2.4.1.2 Ensure access to /etc/crontab is configured   2.4.1.3 Ensure access to /etc/cron.hourly is configured   2.4.1.4 Ensure access to /etc/cron.daily is configured   2.4.1.5 Ensure access to /etc/cron.weekly is configured   2.4.1.6 Ensure access to /etc/cron.monthly is configured   2.4.1.8 Ensure access to /etc/cron.d is configured   2.4.1.9 Ensure access to crontab is configured   2.4.2.1 Ensure access to at is configured   3.1.1 Ensure IPv6 status is identified   3.1.2 Ensure wireless interfaces are not available   3.1.3 Ensure bluetooth services are not in use   3.2.1 Ensure dccp kernel module is not available   3.2.2 Ensure tipc kernel module is not available   3.2.3 Ensure rds kernel module is not available   3.2.4 Ensure sctp kernel module is not available   Page 963 Internal Only - General Recommendation Set Correctly Yes No 3.3.1.1 Ensure net.ipv4.ip_forward is configured   3.3.1.2 Ensure net.ipv4.conf.all.forwarding is configured   3.3.1.3 Ensure net.ipv4.conf.default.forwarding is configured   3.3.1.4 Ensure net.ipv4.conf.all.send_redirects is configured   3.3.1.5 Ensure net.ipv4.conf.default.send_redirects is configured   3.3.1.6 Ensure net.ipv4.icmp_ignore_bogus_error_responses is   configured 3.3.1.7 Ensure net.ipv4.icmp_echo_ignore_broadcasts is   configured 3.3.1.8 Ensure net.ipv4.conf.all.accept_redirects is configured   3.3.1.9 Ensure net.ipv4.conf.default.accept_redirects is   configured 3.3.1.10 Ensure net.ipv4.conf.all.secure_redirects is configured   3.3.1.11 Ensure net.ipv4.conf.default.secure_redirects is   configured 3.3.1.12 Ensure net.ipv4.conf.all.rp_filter is configured   3.3.1.13 Ensure net.ipv4.conf.default.rp_filter is configured   3.3.1.14 Ensure net.ipv4.conf.all.accept_source_route is   configured 3.3.1.15 Ensure net.ipv4.conf.default.accept_source_route is   configured 3.3.1.16 Ensure net.ipv4.conf.all.log_martians is configured   3.3.1.17 Ensure net.ipv4.conf.default.log_martians is configured   3.3.1.18 Ensure net.ipv4.tcp_syncookies is configured   3.3.2.1 Ensure net.ipv6.conf.all.forwarding is configured   3.3.2.2 Ensure net.ipv6.conf.default.forwarding is configured   3.3.2.3 Ensure net.ipv6.conf.all.accept_redirects is configured   3.3.2.4 Ensure net.ipv6.conf.default.accept_redirects is   configured 3.3.2.5 Ensure net.ipv6.conf.all.accept_source_route is   configured 3.3.2.6 Ensure net.ipv6.conf.default.accept_source_route is   configured 3.3.2.7 Ensure net.ipv6.conf.all.accept_ra is configured   3.3.2.8 Ensure net.ipv6.conf.default.accept_ra is configured   4.1.1 Ensure ufw is installed   4.1.2 Ensure ufw service is configured   4.1.3 Ensure ufw incoming default is configured   4.1.4 Ensure ufw outgoing default is configured   4.1.5 Ensure ufw routed default is configured   5.1.1 Ensure access to /etc/ssh/sshd_config is configured   Page 964 Internal Only - General Recommendation Set Correctly Yes No 5.1.2 Ensure access to SSH private host key files is configured   5.1.3 Ensure access to SSH public host key files is configured   5.1.4 Ensure sshd access is configured   5.1.6 Ensure sshd Ciphers are configured   5.1.8 Ensure sshd DisableForwarding is enabled   5.1.9 Ensure sshd GSSAPIAuthentication is disabled   5.1.10 Ensure sshd HostbasedAuthentication is disabled   5.1.11 Ensure sshd IgnoreRhosts is enabled   5.1.12 Ensure sshd KexAlgorithms is configured   5.1.14 Ensure sshd LogLevel is configured   5.1.15 Ensure sshd MACs are configured   5.1.16 Ensure sshd MaxAuthTries is configured   5.1.19 Ensure sshd PermitEmptyPasswords is disabled   5.1.20 Ensure sshd PermitRootLogin is disabled   5.1.22 Ensure sshd UsePAM is enabled   5.2.1 Ensure sudo is installed   5.2.2 Ensure sudo commands use pty   5.2.3 Ensure sudo log file exists   5.2.4 Ensure users must provide password for escalation   5.2.5 Ensure re-authentication for privilege escalation is not   disabled globally 5.2.6 Ensure sudo timestamp_timeout is configured   5.2.7 Ensure access to the su command is restricted   5.3.1.3 Ensure latest version of libpam-pwquality is installed   5.3.2.1 Ensure pam_unix module is enabled   5.3.2.2 Ensure pam_faillock module is enabled   5.3.2.3 Ensure pam_pwquality module is enabled   5.3.2.4 Ensure pam_pwhistory module is enabled   5.3.3.1.1 Ensure password failed attempts lockout is configured   5.3.3.1.2 Ensure password unlock time is configured   5.3.3.1.3 Ensure password failed attempts lockout includes root   account 5.3.3.2.1 Ensure password number of changed characters is   configured 5.3.3.2.2 Ensure minimum password length is configured   5.3.3.2.3 Ensure password complexity is configured   5.3.3.2.4 Ensure password same consecutive characters is   configured 5.3.3.2.5 Ensure password maximum sequential characters is   configured 5.3.3.2.6 Ensure password dictionary check is enabled   Page 965 Internal Only - General Recommendation Set Correctly Yes No 5.3.3.2.7 Ensure password quality checking is enforced   5.3.3.2.8 Ensure password quality is enforced for the root user   5.3.3.3.1 Ensure password history remember is configured   5.3.3.3.2 Ensure password history is enforced for the root user   5.3.3.3.3 Ensure pam_pwhistory includes use_authtok   5.3.3.4.1 Ensure pam_unix does not include nullok   5.3.3.4.2 Ensure pam_unix does not include remember   5.3.3.4.3 Ensure pam_unix includes a strong password hashing   algorithm 5.3.3.4.4 Ensure pam_unix includes use_authtok   5.4.1.1 Ensure password expiration is configured   5.4.1.2 Ensure minimum password days is configured   5.4.1.3 Ensure password expiration warning days is configured   5.4.1.4 Ensure strong password hashing algorithm is configured   5.4.1.5 Ensure inactive password lock is configured   5.4.1.6 Ensure all users last password change date is in the past   5.4.2.1 Ensure root is the only UID 0 account   5.4.2.2 Ensure root is the only GID 0 account   5.4.2.3 Ensure group root is the only GID 0 group   5.4.2.4 Ensure root account access is controlled   5.4.2.6 Ensure root user umask is configured   5.4.2.7 Ensure system accounts do not have a valid login shell   5.4.2.8 Ensure accounts without a valid login shell are locked   5.4.3.2 Ensure default user shell timeout is configured   5.4.3.3 Ensure default user umask is configured   6.1.1.1.1 Ensure journald service is active   6.1.1.1.2 Ensure journald log file access is configured   6.1.1.1.3 Ensure journald log file rotation is configured   6.1.1.1.4 Ensure journald ForwardToSyslog is disabled   6.1.1.1.5 Ensure journald Storage is configured   6.1.1.1.6 Ensure journald Compress is configured   6.1.1.2.1 Ensure systemd-journal-remote is installed   6.1.1.2.2 Ensure systemd-journal-upload authentication is   configured 6.1.1.2.3 Ensure systemd-journal-upload is enabled and active   6.1.1.2.4 Ensure systemd-journal-remote service is not in use   6.1.2.1 Ensure rsyslog is installed   6.1.2.2 Ensure rsyslog service is enabled and active   6.1.2.3 Ensure journald is configured to send logs to rsyslog   6.1.2.4 Ensure rsyslog log file creation mode is configured   Page 966 Internal Only - General Recommendation Set Correctly Yes No 6.1.2.5 Ensure rsyslog logging is configured   6.1.2.6 Ensure rsyslog is configured to send logs to a remote log   host 6.1.2.7 Ensure rsyslog is not configured to receive logs from a   remote client 6.1.2.8 Ensure logrotate is configured   6.1.3.1 Ensure access to all logfiles has been configured   6.2.1.1 Ensure auditd packages are installed   6.2.1.2 Ensure auditd service is enabled and active   6.2.1.3 Ensure auditing for processes that start prior to auditd is   enabled 6.2.1.4 Ensure audit_backlog_limit is configured   6.2.2.1 Ensure audit log storage size is configured   6.2.2.2 Ensure audit logs are not automatically deleted   6.2.2.3 Ensure system is disabled when audit logs are full   6.2.2.4 Ensure system warns when audit logs are low on space   6.2.3.1 Ensure changes to system administration scope   (sudoers) is collected 6.2.3.2 Ensure actions as another user are always logged   6.2.3.3 Ensure events that modify the sudo log file are collected   6.2.3.4 Ensure events that modify date and time information are   collected 6.2.3.5 Ensure events that modify the system's network   environment are collected 6.2.3.6 Ensure use of privileged commands are collected   6.2.3.7 Ensure unsuccessful file access attempts are collected   6.2.3.8 Ensure events that modify user/group information are   collected 6.2.3.9 Ensure discretionary access control permission   modification events are collected 6.2.3.10 Ensure successful file system mounts are collected   6.2.3.11 Ensure session initiation information is collected   6.2.3.12 Ensure login and logout events are collected   6.2.3.13 Ensure file deletion events by users are collected   6.2.3.14 Ensure events that modify the system's Mandatory   Access Controls are collected 6.2.3.15 Ensure successful and unsuccessful attempts to use the   chcon command are collected 6.2.3.16 Ensure successful and unsuccessful attempts to use the   setfacl command are collected Page 967 Internal Only - General Recommendation Set Correctly Yes No 6.2.3.17 Ensure successful and unsuccessful attempts to use the   chacl command are collected 6.2.3.18 Ensure successful and unsuccessful attempts to use the   usermod command are collected 6.2.3.19 Ensure kernel module loading unloading and modification   is collected 6.2.3.20 Ensure the audit configuration is immutable   6.2.3.21 Ensure the running and on disk configuration is the same   6.2.4.1 Ensure audit log files mode is configured   6.2.4.2 Ensure audit log files owner is configured   6.2.4.3 Ensure audit log files group owner is configured   6.2.4.4 Ensure the audit log file directory mode is configured   6.2.4.5 Ensure audit configuration files mode is configured   6.2.4.6 Ensure audit configuration files owner is configured   6.2.4.7 Ensure audit configuration files group owner is   configured 6.2.4.8 Ensure audit tools mode is configured   6.2.4.9 Ensure audit tools owner is configured   6.2.4.10 Ensure audit tools group owner is configured   6.3.1 Ensure AIDE is installed   6.3.2 Ensure filesystem integrity is regularly checked   7.1.1 Ensure access to /etc/passwd is configured   7.1.2 Ensure access to /etc/passwd- is configured   7.1.3 Ensure access to /etc/group is configured   7.1.4 Ensure access to /etc/group- is configured   7.1.5 Ensure access to /etc/shadow is configured   7.1.6 Ensure access to /etc/shadow- is configured   7.1.7 Ensure access to /etc/gshadow is configured   7.1.8 Ensure access to /etc/gshadow- is configured   7.1.9 Ensure access to /etc/shells is configured   7.1.10 Ensure access to /etc/security/opasswd is configured   7.1.11 Ensure world writable files and directories are secured   7.1.12 Ensure no files or directories without an owner and a   group exist 7.1.13 Ensure SUID and SGID files are reviewed   7.2.1 Ensure accounts in /etc/passwd use shadowed   passwords 7.2.2 Ensure /etc/shadow password fields are not empty   7.2.3 Ensure all groups in /etc/passwd exist in /etc/group   7.2.4 Ensure shadow group is empty   Page 968 Internal Only - General Recommendation Set Correctly Yes No 7.2.9 Ensure local interactive user home directories are   configured 7.2.10 Ensure local interactive user dot files access is   configured Page 969 Internal Only - General Appendix: CIS Controls v8 Unmapped Recommendations Recommendation Set Correctly Yes No 1.7.2 Ensure GDM login banner is configured   1.7.3 Ensure GDM disable-user-list option is enabled   1.7.7 Ensure GDM disabling automatic mounting of removable   media is not overridden 2.4.1.7 Ensure access to /etc/cron.yearly is configured   Page 970 Internal Only - General Appendix: Change History Date Version Changes for this version ADDED: ADDED RECOMMENDATION: 1.1.1.10 - Ensure unused filesystems kernel modules are not 10/30/2025 3.0.0 available 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.1.1.11 - Ensure firewire-core kernel module is not available 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.1.1.6 - Ensure overlay kernel module is not available 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.1.2.1.1 - Ensure /tmp is tmpfs or a separate partition 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.1.2.2.1 - Ensure /dev/shm is tmpfs or a separate partition 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.3.1.1 - Ensure the apparmor packages are installed 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.3.1.2 - Ensure AppArmor is enabled 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.3.1.3 - Ensure all AppArmor Profiles are not disabled 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.5.1 - Ensure randomize_va_space is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.5.2 - Ensure ptrace_scope is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.5.3 - Ensure suid_dumpable is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.5.4 - Ensure core file size is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.5.6 - Ensure Automatic Error Reporting is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.6.1 - Ensure /etc/motd is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.6.2 - Ensure /etc/issue is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.6.3 - Ensure /etc/issue.net is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.7.10 - Ensure XDMCP is not enabled 10/30/2025 3.0.0 ADDED RECOMMENDATION: 1.7.11 - Ensure Xwayland is configured ADDED RECOMMENDATION: 2.1.21 - Ensure mail transfer agents are configured for local- 10/30/2025 3.0.0 only mode 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.2.1 - Ensure nis client is not installed 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.2 - Ensure access to /etc/crontab is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.3 - Ensure access to /etc/cron.hourly is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.4 - Ensure access to /etc/cron.daily is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.5 - Ensure access to /etc/cron.weekly is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.6 - Ensure access to /etc/cron.monthly is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.7 - Ensure access to /etc/cron.yearly is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.8 - Ensure access to /etc/cron.d is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.1.9 - Ensure access to crontab is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 2.4.2.1 - Ensure access to at is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.1.2 - Ensure wireless interfaces are not available 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.1 - Ensure net.ipv4.ip_forward is configured ADDED RECOMMENDATION: 3.3.1.10 - Ensure net.ipv4.conf.all.secure_redirects is 10/30/2025 3.0.0 configured ADDED RECOMMENDATION: 3.3.1.11 - Ensure net.ipv4.conf.default.secure_redirects is 10/30/2025 3.0.0 configured Page 971 Internal Only - General 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.12 - Ensure net.ipv4.conf.all.rp_filter is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.13 - Ensure net.ipv4.conf.default.rp_filter is configured ADDED RECOMMENDATION: 3.3.1.14 - Ensure net.ipv4.conf.all.accept_source_route is 10/30/2025 3.0.0 configured ADDED RECOMMENDATION: 3.3.1.15 - Ensure net.ipv4.conf.default.accept_source_route is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.16 - Ensure net.ipv4.conf.all.log_martians is configured ADDED RECOMMENDATION: 3.3.1.17 - Ensure net.ipv4.conf.default.log_martians is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.18 - Ensure net.ipv4.tcp_syncookies is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.2 - Ensure net.ipv4.conf.all.forwarding is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.3 - Ensure net.ipv4.conf.default.forwarding is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.4 - Ensure net.ipv4.conf.all.send_redirects is configured ADDED RECOMMENDATION: 3.3.1.5 - Ensure net.ipv4.conf.default.send_redirects is 10/30/2025 3.0.0 configured ADDED RECOMMENDATION: 3.3.1.6 - Ensure net.ipv4.icmp_ignore_bogus_error_responses 10/30/2025 3.0.0 is configured ADDED RECOMMENDATION: 3.3.1.7 - Ensure net.ipv4.icmp_echo_ignore_broadcasts is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.1.8 - Ensure net.ipv4.conf.all.accept_redirects is configured ADDED RECOMMENDATION: 3.3.1.9 - Ensure net.ipv4.conf.default.accept_redirects is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.2.1 - Ensure net.ipv6.conf.all.forwarding is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.2.2 - Ensure net.ipv6.conf.default.forwarding is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.2.3 - Ensure net.ipv6.conf.all.accept_redirects is configured ADDED RECOMMENDATION: 3.3.2.4 - Ensure net.ipv6.conf.default.accept_redirects is 10/30/2025 3.0.0 configured ADDED RECOMMENDATION: 3.3.2.5 - Ensure net.ipv6.conf.all.accept_source_route is 10/30/2025 3.0.0 configured ADDED RECOMMENDATION: 3.3.2.6 - Ensure net.ipv6.conf.default.accept_source_route is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.2.7 - Ensure net.ipv6.conf.all.accept_ra is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 3.3.2.8 - Ensure net.ipv6.conf.default.accept_ra is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 4.1.2 - Ensure ufw service is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 4.1.3 - Ensure ufw incoming default is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 4.1.4 - Ensure ufw outgoing default is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 4.1.5 - Ensure ufw routed default is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.1.1 - Ensure access to /etc/ssh/sshd_config is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.1.2 - Ensure access to SSH private host key files is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.1.3 - Ensure access to SSH public host key files is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.2.4 - Ensure users must provide password for escalation 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.2.6 - Ensure sudo timestamp_timeout is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.3.1.2 - Ensure latest version of libpam-modules is installed 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.3.1.3 - Ensure latest version of libpam-pwquality is installed Page 972 Internal Only - General 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.4.1.2 - Ensure minimum password days is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 5.4.2.4 - Ensure root account access is controlled 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.1.1.1 - Ensure journald service is active ADDED RECOMMENDATION: 6.1.1.2.2 - Ensure systemd-journal-upload authentication is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.1 - Ensure rsyslog is installed 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.2 - Ensure rsyslog service is enabled and active 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.3 - Ensure journald is configured to send logs to rsyslog 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.4 - Ensure rsyslog log file creation mode is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.5 - Ensure rsyslog logging is configured ADDED RECOMMENDATION: 6.1.2.6 - Ensure rsyslog is configured to send logs to a remote 10/30/2025 3.0.0 log host ADDED RECOMMENDATION: 6.1.2.7 - Ensure rsyslog is not configured to receive logs from a 10/30/2025 3.0.0 remote client 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.1.2.8 - Ensure logrotate is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 6.2.1.4 - Ensure audit_backlog_limit is configured ADDED RECOMMENDATION: 6.2.3.15 - Ensure successful and unsuccessful attempts to use 10/30/2025 3.0.0 the chcon command are collected ADDED RECOMMENDATION: 6.2.3.16 - Ensure successful and unsuccessful attempts to use 10/30/2025 3.0.0 the setfacl command are collected ADDED RECOMMENDATION: 6.2.3.17 - Ensure successful and unsuccessful attempts to use 10/30/2025 3.0.0 the chacl command are collected ADDED RECOMMENDATION: 6.2.3.18 - Ensure successful and unsuccessful attempts to use 10/30/2025 3.0.0 the usermod command are collected 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.1 - Ensure access to /etc/passwd is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.10 - Ensure access to /etc/security/opasswd is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.2 - Ensure access to /etc/passwd- is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.3 - Ensure access to /etc/group is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.4 - Ensure access to /etc/group- is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.5 - Ensure access to /etc/shadow is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.6 - Ensure access to /etc/shadow- is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.7 - Ensure access to /etc/gshadow is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.8 - Ensure access to /etc/gshadow- is configured 10/30/2025 3.0.0 ADDED RECOMMENDATION: 7.1.9 - Ensure access to /etc/shells is configured 10/30/2025 3.0.0 ADDED SECTION: 3.3.1 - Configure IPv4 parameters 10/30/2025 3.0.0 ADDED SECTION: 3.3.2 - Configure IPv6 parameters 10/30/2025 3.0.0 ADDED SECTION: 4.1 - Configure Uncomplicated Firewall 10/30/2025 3.0.0 ADDED SECTION: 6.1.2 - Configure rsyslog 10/30/2025 3.0.0 ADDED SECTION: 7.1 - Configure system file and directory access DROPPED: 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.1.2.1.1 - Ensure /tmp is a separate partition 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.1.2.2.1 - Ensure /dev/shm is a separate partition 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.3.1.1 - Ensure AppArmor is installed Page 973 Internal Only - General DROPPED RECOMMENDATION: 1.3.1.2 - Ensure AppArmor is enabled in the bootloader 10/30/2025 3.0.0 configuration DROPPED RECOMMENDATION: 1.3.1.3 - Ensure all AppArmor Profiles are in enforce or 10/30/2025 3.0.0 complain mode DROPPED RECOMMENDATION: 1.5.1 - Ensure address space layout randomization is 10/30/2025 3.0.0 enabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.5.2 - Ensure ptrace_scope is restricted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.5.3 - Ensure core dumps are restricted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.5.5 - Ensure Automatic Error Reporting is not enabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.6.1 - Ensure message of the day is configured properly DROPPED RECOMMENDATION: 1.6.2 - Ensure local login warning banner is configured 10/30/2025 3.0.0 properly DROPPED RECOMMENDATION: 1.6.3 - Ensure remote login warning banner is configured 10/30/2025 3.0.0 properly 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 1.7.10 - Ensure XDCMP is not enabled DROPPED RECOMMENDATION: 2.1.21 - Ensure mail transfer agent is configured for local- 10/30/2025 3.0.0 only mode 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 2.2.1 - Ensure NIS Client is not installed 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 2.4.1.2 - Ensure permissions on /etc/crontab are configured DROPPED RECOMMENDATION: 2.4.1.3 - Ensure permissions on /etc/cron.hourly are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 2.4.1.4 - Ensure permissions on /etc/cron.daily are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 2.4.1.5 - Ensure permissions on /etc/cron.weekly are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 2.4.1.6 - Ensure permissions on /etc/cron.monthly are 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 2.4.1.7 - Ensure permissions on /etc/cron.d are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 2.4.1.8 - Ensure crontab is restricted to authorized users 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 2.4.2.1 - Ensure at is restricted to authorized users 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.1.2 - Ensure wireless interfaces are disabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.1 - Ensure ip forwarding is disabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.10 - Ensure tcp syn cookies is enabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.11 - Ensure ipv6 router advertisements are not accepted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.2 - Ensure packet redirect sending is disabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.3 - Ensure bogus icmp responses are ignored 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.4 - Ensure broadcast icmp requests are ignored 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.5 - Ensure icmp redirects are not accepted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.6 - Ensure secure icmp redirects are not accepted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.7 - Ensure reverse path filtering is enabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.8 - Ensure source routed packets are not accepted 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 3.3.9 - Ensure suspicious packets are logged 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.2 - Ensure iptables-persistent is not installed with ufw 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.3 - Ensure ufw service is enabled Page 974 Internal Only - General 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.4 - Ensure ufw loopback traffic is configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.5 - Ensure ufw outbound connections are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.6 - Ensure ufw firewall rules exist for all open ports 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.1.7 - Ensure ufw default deny firewall policy 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.1 - Ensure nftables is installed 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.10 - Ensure nftables rules are permanent 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.2 - Ensure ufw is uninstalled or disabled with nftables 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.3 - Ensure iptables are flushed with nftables 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.4 - Ensure a nftables table exists 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.5 - Ensure nftables base chains exist 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.6 - Ensure nftables loopback traffic is configured DROPPED RECOMMENDATION: 4.2.7 - Ensure nftables outbound and established 10/30/2025 3.0.0 connections are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.8 - Ensure nftables default deny firewall policy 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.2.9 - Ensure nftables service is enabled 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.1.1 - Ensure iptables packages are installed 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.1.2 - Ensure nftables is not installed with iptables 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.1.3 - Ensure ufw is uninstalled or disabled with iptables 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.2.1 - Ensure iptables default deny firewall policy 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.2.2 - Ensure iptables loopback traffic is configured DROPPED RECOMMENDATION: 4.3.2.3 - Ensure iptables outbound and established 10/30/2025 3.0.0 connections are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.2.4 - Ensure iptables firewall rules exist for all open ports 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.3.1 - Ensure ip6tables default deny firewall policy 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 4.3.3.2 - Ensure ip6tables loopback traffic is configured DROPPED RECOMMENDATION: 4.3.3.3 - Ensure ip6tables outbound and established 10/30/2025 3.0.0 connections are configured DROPPED RECOMMENDATION: 4.3.3.4 - Ensure ip6tables firewall rules exist for all open 10/30/2025 3.0.0 ports DROPPED RECOMMENDATION: 5.1.1 - Ensure permissions on /etc/ssh/sshd_config are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 5.1.2 - Ensure permissions on SSH private host key files are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 5.1.3 - Ensure permissions on SSH public host key files are 10/30/2025 3.0.0 configured DROPPED RECOMMENDATION: 5.2.4 - Ensure users must provide password for privilege 10/30/2025 3.0.0 escalation DROPPED RECOMMENDATION: 5.2.6 - Ensure sudo authentication timeout is configured 10/30/2025 3.0.0 correctly 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 5.3.1.2 - Ensure libpam-modules is installed 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 5.3.1.3 - Ensure libpam-pwquality is installed 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 5.4.1.2 - Ensure minimum password age is configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 5.4.2.4 - Ensure root password is set Page 975 Internal Only - General 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 6.2.1.1.1 - Ensure journald service is enabled and active DROPPED RECOMMENDATION: 6.2.1.2.2 - Ensure systemd-journal-remote authentication is 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 6.3.1.4 - Ensure audit_backlog_limit is sufficient DROPPED RECOMMENDATION: 6.3.3.15 - Ensure successful and unsuccessful attempts to 10/30/2025 3.0.0 use the chcon command are recorded DROPPED RECOMMENDATION: 6.3.3.16 - Ensure successful and unsuccessful attempts to 10/30/2025 3.0.0 use the setfacl command are recorded DROPPED RECOMMENDATION: 6.3.3.17 - Ensure successful and unsuccessful attempts to 10/30/2025 3.0.0 use the chacl command are recorded DROPPED RECOMMENDATION: 6.3.3.18 - Ensure successful and unsuccessful attempts to 10/30/2025 3.0.0 use the usermod command are recorded 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.1 - Ensure permissions on /etc/passwd are configured DROPPED RECOMMENDATION: 7.1.10 - Ensure permissions on /etc/security/opasswd are 10/30/2025 3.0.0 configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.2 - Ensure permissions on /etc/passwd- are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.3 - Ensure permissions on /etc/group are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.4 - Ensure permissions on /etc/group- are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.5 - Ensure permissions on /etc/shadow are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.6 - Ensure permissions on /etc/shadow- are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.7 - Ensure permissions on /etc/gshadow are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.8 - Ensure permissions on /etc/gshadow- are configured 10/30/2025 3.0.0 DROPPED RECOMMENDATION: 7.1.9 - Ensure permissions on /etc/shells are configured 10/30/2025 3.0.0 DROPPED SECTION: 4.1 - Configure UncomplicatedFirewall 10/30/2025 3.0.0 DROPPED SECTION: 4.2 - Configure nftables 10/30/2025 3.0.0 DROPPED SECTION: 4.3 - Configure iptables 10/30/2025 3.0.0 DROPPED SECTION: 4.3.1 - Configure iptables software 10/30/2025 3.0.0 DROPPED SECTION: 4.3.2 - Configure IPv4 iptables 10/30/2025 3.0.0 DROPPED SECTION: 4.3.3 - Configure IPv6 ip6tables 10/30/2025 3.0.0 DROPPED SECTION: 7.1 - System File Permissions MOVED: MOVED RECOMMENDATION: 1.1.1.7 - Ensure squashfs kernel module is not available moved 10/30/2025 3.0.0 from 1.1.1.6 in 2.0.0 MOVED RECOMMENDATION: 1.1.1.8 - Ensure udf kernel module is not available moved from 10/30/2025 3.0.0 1.1.1.7 in 2.0.0 MOVED RECOMMENDATION: 1.1.1.9 - Ensure usb-storage kernel module is not available 10/30/2025 3.0.0 moved from 1.1.1.8 in 2.0.0 10/30/2025 3.0.0 MOVED RECOMMENDATION: 1.5.5 - Ensure prelink is not installed moved from 1.5.4 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.1.2 - Ensure journald log file access is configured moved 10/30/2025 3.0.0 from 6.2.1.1.2 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.1.3 - Ensure journald log file rotation is configured moved 10/30/2025 3.0.0 from 6.2.1.1.3 in 2.0.0 Page 976 Internal Only - General MOVED RECOMMENDATION: 6.1.1.1.4 - Ensure journald ForwardToSyslog is disabled moved 10/30/2025 3.0.0 from 6.2.1.1.4 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.1.5 - Ensure journald Storage is configured moved from 10/30/2025 3.0.0 6.2.1.1.5 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.1.6 - Ensure journald Compress is configured moved from 10/30/2025 3.0.0 6.2.1.1.6 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.2.1 - Ensure systemd-journal-remote is installed moved 10/30/2025 3.0.0 from 6.2.1.2.1 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.2.3 - Ensure systemd-journal-upload is enabled and 10/30/2025 3.0.0 active moved from 6.2.1.2.3 in 2.0.0 MOVED RECOMMENDATION: 6.1.1.2.4 - Ensure systemd-journal-remote service is not in use 10/30/2025 3.0.0 moved from 6.2.1.2.4 in 2.0.0 MOVED RECOMMENDATION: 6.1.3.1 - Ensure access to all logfiles has been configured 10/30/2025 3.0.0 moved from 6.2.2.1 in 2.0.0 MOVED RECOMMENDATION: 6.2.1.1 - Ensure auditd packages are installed moved from 10/30/2025 3.0.0 6.3.1.1 in 2.0.0 MOVED RECOMMENDATION: 6.2.1.2 - Ensure auditd service is enabled and active moved 10/30/2025 3.0.0 from 6.3.1.2 in 2.0.0 MOVED RECOMMENDATION: 6.2.1.3 - Ensure auditing for processes that start prior to auditd 10/30/2025 3.0.0 is enabled moved from 6.3.1.3 in 2.0.0 MOVED RECOMMENDATION: 6.2.2.1 - Ensure audit log storage size is configured moved from 10/30/2025 3.0.0 6.3.2.1 in 2.0.0 MOVED RECOMMENDATION: 6.2.2.2 - Ensure audit logs are not automatically deleted moved 10/30/2025 3.0.0 from 6.3.2.2 in 2.0.0 MOVED RECOMMENDATION: 6.2.2.3 - Ensure system is disabled when audit logs are full 10/30/2025 3.0.0 moved from 6.3.2.3 in 2.0.0 MOVED RECOMMENDATION: 6.2.2.4 - Ensure system warns when audit logs are low on 10/30/2025 3.0.0 space moved from 6.3.2.4 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.1 - Ensure changes to system administration scope 10/30/2025 3.0.0 (sudoers) is collected moved from 6.3.3.1 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.10 - Ensure successful file system mounts are collected 10/30/2025 3.0.0 moved from 6.3.3.10 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.11 - Ensure session initiation information is collected 10/30/2025 3.0.0 moved from 6.3.3.11 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.12 - Ensure login and logout events are collected moved 10/30/2025 3.0.0 from 6.3.3.12 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.13 - Ensure file deletion events by users are collected 10/30/2025 3.0.0 moved from 6.3.3.13 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.14 - Ensure events that modify the system's Mandatory 10/30/2025 3.0.0 Access Controls are collected moved from 6.3.3.14 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.19 - Ensure kernel module loading unloading and 10/30/2025 3.0.0 modification is collected moved from 6.3.3.19 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.2 - Ensure actions as another user are always logged 10/30/2025 3.0.0 moved from 6.3.3.2 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.20 - Ensure the audit configuration is immutable moved 10/30/2025 3.0.0 from 6.3.3.20 in 2.0.0 Page 977 Internal Only - General MOVED RECOMMENDATION: 6.2.3.21 - Ensure the running and on disk configuration is the 10/30/2025 3.0.0 same moved from 6.3.3.21 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.3 - Ensure events that modify the sudo log file are 10/30/2025 3.0.0 collected moved from 6.3.3.3 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.4 - Ensure events that modify date and time information 10/30/2025 3.0.0 are collected moved from 6.3.3.4 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.5 - Ensure events that modify the system's network 10/30/2025 3.0.0 environment are collected moved from 6.3.3.5 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.6 - Ensure use of privileged commands are collected 10/30/2025 3.0.0 moved from 6.3.3.6 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.7 - Ensure unsuccessful file access attempts are 10/30/2025 3.0.0 collected moved from 6.3.3.7 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.8 - Ensure events that modify user/group information are 10/30/2025 3.0.0 collected moved from 6.3.3.8 in 2.0.0 MOVED RECOMMENDATION: 6.2.3.9 - Ensure discretionary access control permission 10/30/2025 3.0.0 modification events are collected moved from 6.3.3.9 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.1 - Ensure audit log files mode is configured moved from 10/30/2025 3.0.0 6.3.4.1 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.10 - Ensure audit tools group owner is configured moved 10/30/2025 3.0.0 from 6.3.4.10 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.2 - Ensure audit log files owner is configured moved from 10/30/2025 3.0.0 6.3.4.2 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.3 - Ensure audit log files group owner is configured moved 10/30/2025 3.0.0 from 6.3.4.3 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.4 - Ensure the audit log file directory mode is configured 10/30/2025 3.0.0 moved from 6.3.4.4 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.5 - Ensure audit configuration files mode is configured 10/30/2025 3.0.0 moved from 6.3.4.5 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.6 - Ensure audit configuration files owner is configured 10/30/2025 3.0.0 moved from 6.3.4.6 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.7 - Ensure audit configuration files group owner is 10/30/2025 3.0.0 configured moved from 6.3.4.7 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.8 - Ensure audit tools mode is configured moved from 10/30/2025 3.0.0 6.3.4.8 in 2.0.0 MOVED RECOMMENDATION: 6.2.4.9 - Ensure audit tools owner is configured moved from 10/30/2025 3.0.0 6.3.4.9 in 2.0.0 10/30/2025 3.0.0 MOVED RECOMMENDATION: 6.3.1 - Ensure AIDE is installed moved from 6.1.1 in 2.0.0 MOVED RECOMMENDATION: 6.3.2 - Ensure filesystem integrity is regularly checked moved 10/30/2025 3.0.0 from 6.1.2 in 2.0.0 MOVED RECOMMENDATION: 6.3.3 - Ensure cryptographic mechanisms are used to protect 10/30/2025 3.0.0 the integrity of audit tools moved from 6.1.3 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.1 - System Logging moved from 6.2 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.1.1 - Configure journald moved from 6.2.1 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.1.1.1 - Configure systemd-journald service moved from 6.2.1.1 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.1.1.2 - Configure systemd-journal-remote moved from 6.2.1.2 in 2.0.0 Page 978 Internal Only - General 10/30/2025 3.0.0 MOVED SECTION: 6.1.3 - Configure Logfiles moved from 6.2.2 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.2 - System Auditing moved from 6.3 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.2.1 - Configure auditd Service moved from 6.3.1 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.2.2 - Configure Data Retention moved from 6.3.2 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.2.3 - Configure auditd Rules moved from 6.3.3 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.2.4 - Configure auditd File Access moved from 6.3.4 in 2.0.0 10/30/2025 3.0.0 MOVED SECTION: 6.3 - Configure Filesystem Integrity Checking moved from 6.1 in 2.0.0 UPDATED: UPDATED RECOMMENDATION: 1.1.1.7 - Ensure squashfs kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.8 - Ensure udf kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.9 - Ensure usb-storage kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.1.2 - Ensure journald log file access is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 6.1.1.1.3 - Ensure journald log file rotation is configured - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.1.4 - Ensure journald ForwardToSyslog is disabled - 10/30/2025 3.0.0 Sections Modified: Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.1.5 - Ensure journald Storage is configured - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.1.6 - Ensure journald Compress is configured - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.2.1 - Ensure systemd-journal-remote is installed - 10/30/2025 3.0.0 Sections Modified: Rationale Statement; Audit Procedure UPDATED RECOMMENDATION: 6.1.1.2.4 - Ensure systemd-journal-remote service is not in 10/30/2025 3.0.0 use - Sections Modified: Description; Rationale Statement; Audit Procedure UPDATED RECOMMENDATION: 6.1.3.1 - Ensure access to all logfiles has been configured - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.2.3.1 - Ensure changes to system administration scope 10/30/2025 3.0.0 (sudoers) is collected - Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 6.2.3.19 - Ensure kernel module loading unloading and modification is collected - Sections Modified: Description; Remediation Procedure; Audit 10/30/2025 3.0.0 Procedure UPDATED RECOMMENDATION: 6.2.3.20 - Ensure the audit configuration is immutable - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 6.2.3.4 - Ensure events that modify date and time 10/30/2025 3.0.0 information are collected - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 6.2.3.5 - Ensure events that modify the system's network 10/30/2025 3.0.0 environment are collected - Sections Modified: Remediation Procedure; Audit Procedure Page 979 Internal Only - General UPDATED RECOMMENDATION: 6.2.4.10 - Ensure audit tools group owner is configured - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 6.2.4.3 - Ensure audit log files group owner is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 6.3.3 - Ensure cryptographic mechanisms are used to protect the integrity of audit tools - Sections Modified: Remediation Procedure; Audit 10/30/2025 3.0.0 Procedure UPDATED RECOMMENDATION: 1.1.1.1 - Ensure cramfs kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.2 - Ensure freevxfs kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.3 - Ensure hfs kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.4 - Ensure hfsplus kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.1.5 - Ensure jffs2 kernel module is not available - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.1.3 - Ensure nosuid option set on /tmp partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.1.4 - Ensure noexec option set on /tmp partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.3.1 - Ensure separate partition exists for /home - 10/30/2025 3.0.0 Sections Modified: Impact Statement; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.3.2 - Ensure nodev option set on /home partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.3.3 - Ensure nosuid option set on /home partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.4.1 - Ensure separate partition exists for /var - Sections 10/30/2025 3.0.0 Modified: Rationale Statement; Impact Statement; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.4.2 - Ensure nodev option set on /var partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.4.3 - Ensure nosuid option set on /var partition - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.1.2.5.1 - Ensure separate partition exists for /var/tmp - 10/30/2025 3.0.0 Sections Modified: Rationale Statement; Impact Statement UPDATED RECOMMENDATION: 1.1.2.7.1 - Ensure separate partition exists for /var/log/audit - 10/30/2025 3.0.0 Sections Modified: Rationale Statement; Impact Statement UPDATED RECOMMENDATION: 1.2.1.1 - Ensure GPG keys are configured - Sections Modified: 10/30/2025 3.0.0 Audit Procedure UPDATED RECOMMENDATION: 1.2.2.1 - Ensure updates, patches, and additional security 10/30/2025 3.0.0 software are installed - Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 1.4.1 - Ensure bootloader password is set - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure Page 980 Internal Only - General UPDATED RECOMMENDATION: 1.7.1 - Ensure GDM is removed - Sections Modified: 10/30/2025 3.0.0 Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.2 - Ensure GDM login banner is configured - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.3 - Ensure GDM disable-user-list option is enabled - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.4 - Ensure GDM screen locks when the user is idle - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.5 - Ensure GDM screen locks cannot be overridden - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.6 - Ensure GDM automatic mounting of removable media 10/30/2025 3.0.0 is disabled - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.7 - Ensure GDM disabling automatic mounting of removable media is not overridden - Sections Modified: Remediation Procedure; Audit 10/30/2025 3.0.0 Procedure UPDATED RECOMMENDATION: 1.7.8 - Ensure GDM autorun-never is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 1.7.9 - Ensure GDM autorun-never is not overridden - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 2.1.18 - Ensure web server services are not in use - Sections 10/30/2025 3.0.0 Modified: Impact Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 2.1.19 - Ensure xinetd services are not in use - Sections 10/30/2025 3.0.0 Modified: Description; Rationale Statement UPDATED RECOMMENDATION: 2.1.4 - Ensure dns server services are not in use - Sections 10/30/2025 3.0.0 Modified: Description; Impact Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 2.1.6 - Ensure ftp server services are not in use - Sections 10/30/2025 3.0.0 Modified: Description; Audit Procedure UPDATED RECOMMENDATION: 2.2.6 - Ensure ftp client is not installed - Sections Modified: 10/30/2025 3.0.0 Description; Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 2.3.1.1 - Ensure a single time synchronization daemon is in 10/30/2025 3.0.0 use - Sections Modified: Description; Audit Procedure UPDATED RECOMMENDATION: 2.3.2.1 - Ensure systemd-timesyncd configured with 10/30/2025 3.0.0 authorized timeserver - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 2.3.2.2 - Ensure systemd-timesyncd is enabled and running - 10/30/2025 3.0.0 Sections Modified: Assessment Status UPDATED RECOMMENDATION: 2.3.3.1 - Ensure chrony is configured with authorized 10/30/2025 3.0.0 timeserver - Sections Modified: Assessment Status; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 3.1.1 - Ensure IPv6 status is identified - Sections Modified: 10/30/2025 3.0.0 Description; Rationale Statement; Audit Procedure UPDATED RECOMMENDATION: 3.1.3 - Ensure bluetooth services are not in use - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 3.2.1 - Ensure dccp kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Profile; Rationale Statement; Remediation Procedure; Audit Procedure Page 981 Internal Only - General UPDATED RECOMMENDATION: 3.2.2 - Ensure tipc kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Profile; Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 3.2.3 - Ensure rds kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Profile; Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 3.2.4 - Ensure sctp kernel module is not available - Sections 10/30/2025 3.0.0 Modified: Profile; Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 4.1.1 - Ensure ufw is installed - Sections Modified: Rationale 10/30/2025 3.0.0 Statement; Impact Statement; Remediation Procedure UPDATED RECOMMENDATION: 5.1.11 - Ensure sshd IgnoreRhosts is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.1.12 - Ensure sshd KexAlgorithms is configured - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 5.1.15 - Ensure sshd MACs are configured - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 5.1.17 - Ensure sshd MaxSessions is configured - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 5.1.18 - Ensure sshd MaxStartups is configured - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 5.1.21 - Ensure sshd PermitUserEnvironment is disabled - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.1.22 - Ensure sshd UsePAM is enabled - Sections Modified: 10/30/2025 3.0.0 Audit Procedure UPDATED RECOMMENDATION: 5.1.4 - Ensure sshd access is configured - Sections Modified: 10/30/2025 3.0.0 Remediation Procedure UPDATED RECOMMENDATION: 5.1.5 - Ensure sshd Banner is configured - Sections Modified: 10/30/2025 3.0.0 Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.1.8 - Ensure sshd DisableForwarding is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.2.2 - Ensure sudo commands use pty - Sections Modified: 10/30/2025 3.0.0 Audit Procedure UPDATED RECOMMENDATION: 5.2.3 - Ensure sudo log file exists - Sections Modified: 10/30/2025 3.0.0 Remediation Procedure UPDATED RECOMMENDATION: 5.3.1.1 - Ensure latest version of pam is installed - Sections 10/30/2025 3.0.0 Modified: Description; Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.2.1 - Ensure pam_unix module is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.2.2 - Ensure pam_faillock module is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure UPDATED RECOMMENDATION: 5.3.2.3 - Ensure pam_pwquality module is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.2.4 - Ensure pam_pwhistory module is enabled - Sections 10/30/2025 3.0.0 Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.3.1.1 - Ensure password failed attempts lockout is 10/30/2025 3.0.0 configured - Sections Modified: Audit Procedure Page 982 Internal Only - General UPDATED RECOMMENDATION: 5.3.3.1.2 - Ensure password unlock time is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.1.3 - Ensure password failed attempts lockout includes 10/30/2025 3.0.0 root account - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.1 - Ensure password number of changed characters 10/30/2025 3.0.0 is configured - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.2 - Ensure minimum password length is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.3 - Ensure password complexity is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.4 - Ensure password same consecutive characters is 10/30/2025 3.0.0 configured - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.5 - Ensure password maximum sequential characters 10/30/2025 3.0.0 is configured - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.6 - Ensure password dictionary check is enabled - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.2.8 - Ensure password quality is enforced for the root 10/30/2025 3.0.0 user - Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 5.3.3.3.1 - Ensure password history remember is configured - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.3.3.2 - Ensure password history is enforced for the root 10/30/2025 3.0.0 user - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.3.3.3 - Ensure pam_pwhistory includes use_authtok - 10/30/2025 3.0.0 Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.3.3.4.1 - Ensure pam_unix does not include nullok - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.4.2 - Ensure pam_unix does not include remember - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.3.3.4.3 - Ensure pam_unix includes a strong password 10/30/2025 3.0.0 hashing algorithm - Sections Modified: Remediation Procedure UPDATED RECOMMENDATION: 5.4.1.1 - Ensure password expiration is configured - Sections 10/30/2025 3.0.0 Modified: Impact Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.4.1.4 - Ensure strong password hashing algorithm is 10/30/2025 3.0.0 configured - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.4.1.5 - Ensure inactive password lock is configured - 10/30/2025 3.0.0 Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.4.1.6 - Ensure all users last password change date is in the 10/30/2025 3.0.0 past - Sections Modified: Audit Procedure UPDATED RECOMMENDATION: 5.4.2.1 - Ensure root is the only UID 0 account - Sections 10/30/2025 3.0.0 Modified: Rationale Statement UPDATED RECOMMENDATION: 5.4.2.5 - Ensure root path integrity - Sections Modified: Audit 10/30/2025 3.0.0 Procedure UPDATED RECOMMENDATION: 5.4.2.6 - Ensure root user umask is configured - Sections 10/30/2025 3.0.0 Modified: Description; Remediation Procedure; Audit Procedure Page 983 Internal Only - General UPDATED RECOMMENDATION: 5.4.3.1 - Ensure nologin is not listed in /etc/shells - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 5.4.3.2 - Ensure default user shell timeout is configured - 10/30/2025 3.0.0 Sections Modified: Description; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 5.4.3.3 - Ensure default user umask is configured - Sections 10/30/2025 3.0.0 Modified: Rationale Statement; Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 7.1.11 - Ensure world writable files and directories are 10/30/2025 3.0.0 secured - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 7.1.13 - Ensure SUID and SGID files are reviewed - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 7.2.10 - Ensure local interactive user dot files access is 10/30/2025 3.0.0 configured - Sections Modified: Remediation Procedure; Audit Procedure UPDATED RECOMMENDATION: 7.2.5 - Ensure no duplicate UIDs exist - Sections Modified: 10/30/2025 3.0.0 Rationale Statement UPDATED RECOMMENDATION: 7.2.7 - Ensure no duplicate user names exist - Sections 10/30/2025 3.0.0 Modified: Audit Procedure UPDATED RECOMMENDATION: 7.2.9 - Ensure local interactive user home directories are 10/30/2025 3.0.0 configured - Sections Modified: Remediation Procedure; Audit Procedure UPDATED SECTION: 1.1.1 - Configure Filesystem Kernel Modules - Sections Modified: 10/30/2025 3.0.0 Description 10/30/2025 3.0.0 UPDATED SECTION: 1.1.2.3 - Configure /home - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 1.2 - Package Management - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 1.2.1 - Configure Package Repositories - Sections Modified: Description UPDATED SECTION: 1.7 - Configure GNOME Display Manager - Sections Modified: 10/30/2025 3.0.0 Description 10/30/2025 3.0.0 UPDATED SECTION: 2.3.2 - Configure systemd-timesyncd - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 2.3.3 - Configure chrony - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 2.4.1 - Configure cron - Sections Modified: Description UPDATED SECTION: 3.3 - Configure Network Kernel Parameters - Sections Modified: 10/30/2025 3.0.0 Description 10/30/2025 3.0.0 UPDATED SECTION: 4 - Host Based Firewall - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 5.1 - Configure SSH Server - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 5.3 - Pluggable Authentication Modules - Sections Modified: Description UPDATED SECTION: 5.3.1 - Configure PAM software packages - Sections Modified: 10/30/2025 3.0.0 Description UPDATED SECTION: 5.4.1 - Configure shadow password suite parameters - Sections 10/30/2025 3.0.0 Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 6.1 - System Logging - Sections Modified: Description 10/30/2025 3.0.0 UPDATED SECTION: 6.2.3 - Configure auditd Rules - Sections Modified: Description UPDATED SECTION: 6.3 - Configure Filesystem Integrity Checking - Sections Modified: 10/30/2025 3.0.0 Description Page 984 Internal Only - General