Creation or Modification of Pluggable Authentication Module or Configuration

Creation or Modification of Pluggable Authentication Module or Configurationedit

This rule monitors for the creation or modification of Pluggable Authentication Module (PAM) shared object files or configuration files. Attackers may create or modify these files to maintain persistence on a compromised system, or harvest account credentials.

Rule type: eql

Rule indices:

logs-endpoint.events.file*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Endpoint
OS: Linux
Use Case: Threat Detection
Tactic: Credential Access
Tactic: Persistence
Data Source: Elastic Defend

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Rule queryedit

file where host.os.type == "linux" and event.action in ("rename", "creation") and
process.executable != null and (
  (file.path : ("/lib/security/*", "/lib64/security/*", "/usr/lib/security/*", "/usr/lib64/security/*",
  "/usr/lib/x86_64-linux-gnu/security/*") and file.extension == "so") or
  (file.path : "/etc/pam.d/*" and file.extension == null) or
  (file.path : "/etc/security/pam_*" or file.path == "/etc/pam.conf")
) and not (
  process.executable in (
    "/bin/dpkg", "/usr/bin/dpkg", "/bin/dockerd", "/usr/bin/dockerd", "/usr/sbin/dockerd", "/bin/microdnf",
    "/usr/bin/microdnf", "/bin/rpm", "/usr/bin/rpm", "/bin/snapd", "/usr/bin/snapd", "/bin/yum", "/usr/bin/yum",
    "/bin/dnf", "/usr/bin/dnf", "/bin/podman", "/usr/bin/podman", "/bin/dnf-automatic", "/usr/bin/dnf-automatic",
    "/bin/pacman", "/usr/bin/pacman", "/usr/bin/dpkg-divert", "/bin/dpkg-divert", "/sbin/apk", "/usr/sbin/apk",
    "/usr/local/sbin/apk", "/usr/bin/apt", "/usr/sbin/pacman", "/bin/podman", "/usr/bin/podman", "/usr/bin/puppet",
    "/bin/puppet", "/opt/puppetlabs/puppet/bin/puppet", "/usr/bin/chef-client", "/bin/chef-client",
    "/bin/autossl_check", "/usr/bin/autossl_check", "/proc/self/exe", "/dev/fd/*",  "/usr/bin/pamac-daemon",
    "/bin/pamac-daemon", "/usr/lib/snapd/snapd", "/usr/local/bin/dockerd", "/usr/sbin/pam-auth-update",
    "/usr/lib/systemd/systemd", "/usr/libexec/packagekitd", "/usr/bin/bsdtar"
  ) or
  file.path : (
    "/tmp/snap.rootfs_*/pam_*.so", "/tmp/newroot/lib/*/pam_*.so", "/tmp/newroot/usr/lib64/security/pam_*.so"
  ) or
  file.extension in ("swp", "swpx", "swx", "dpkg-remove") or
  file.Ext.original.extension == "dpkg-new" or
  process.executable : (
    "/nix/store/*", "/var/lib/dpkg/*", "/snap/*", "/dev/fd/*", "/usr/lib/virtualbox/*"
  ) or
  (process.name == "sed" and file.name : "sed*") or
  (process.name == "perl" and file.name : "e2scrub_all.tmp*")
)

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Create or Modify System Process
- ID: T1543
- Reference URL: https://attack.mitre.org/techniques/T1543/
Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: Modify Authentication Process
- ID: T1556
- Reference URL: https://attack.mitre.org/techniques/T1556/

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