Pluggable Authentication Module (PAM) Creation in Unusual Directory

This rule detects the creation of Pluggable Authentication Module (PAM) shared object files in unusual directories. Attackers may compile PAM shared object files in temporary directories, to move them to system directories later, potentially allowing them to maintain persistence on a compromised system, or harvest account credentials.

Rule type: eql

Rule indices:

logs-endpoint.events.file*

Severity: low

Risk score: 21

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 query

edit

file where host.os.type == "linux" and event.type == "creation" and file.name like "pam_*.so" and not file.path like (
  "/lib/security/*",
  "/lib64/security/*",
  "/lib/x86_64-linux-gnu/security/*",
  "/usr/lib/security/*",
  "/usr/lib64/security/*",
  "/usr/lib/x86_64-linux-gnu/security/*"
) and not (
  process.name in ("dockerd", "containerd", "steam", "buildkitd", "unsquashfs", "pacman") or
  file.path like (
    "/build/rootImage/nix/store/*", "/home/*/.local/share/containers/*", "/nix/store/*", "/var/lib/containerd/*",
    "/var/snap/*", "/usr/share/nix/nix/store/*", "/tmp/cura/squashfs-root/*", "/home/*/docker/*", "/tmp/containerd*"
  )
)

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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