Linux PAM TTY Audit Enabling via /etc/pam.d Modification

Alerts on auditd-observed edits to PAM system-auth/password-auth tied to TTY input auditing.

FreeReviewedSigma · High · v3

Product: linux
Service: auditd
Author: Pawel Mazur (SigmaHQ), DRL 1.1
Published: 2021-05-24
Updated: 2026-07-31

ATT&CK techniques

Cred Access → Collection

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
- T1003OS Credential Dumping
- T1056.001Keylogging
Discovery
Lateral Movement
Collection
- T1056.001Keylogging
C2
Exfiltration
Impact

What it detects

This rule flags Linux auditd PATH and TTY-related events indicating access to PAM configuration files used for system authentication, specifically /etc/pam.d/system-auth and /etc/pam.d/password-auth. Enabling TTY input auditing can support credential collection or keylogging-like behaviors by recording interactive terminal input. The detection relies on auditd telemetry capturing file path activity along with TTY/USER_TTY indicators.

Reporting behind it

Related detections9 linkedT1003 — drag to rearrange

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Suspicious Mimilite Credential Dumper Execution Writing KB-Named Output

Malicious InternalMonologue NTLM Downgrade Execution via process_creation

Suspicious Modification of msDS-KeyCredentialLink for Shadow Credential Abuse

Suspicious Keylogger Capture Database Written to macOS Temp Directory

Possible OxideHarvest Stealer Execution via Combined Short Flag Set

Suspicious Credential Dump Attempt via Task Manager (via process_creation)

Malicious Kong RAT Keylogger Capture File Creation

Linux PAM TTY Audit Enabling via /etc/pam.d Modification

Pivot detection · T1003 · 9 related

Changelog

v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

linux-pam-tty-auditing-change-via-auditd-path-events-49aae26c

title: Linux PAM TTY Audit Enabling via /etc/pam.d Modification
id: d6269d94-960f-4fb3-94b9-e952a59a72c8
status: test
description: This rule flags Linux auditd PATH and TTY-related events indicating access to PAM configuration files used for system authentication, specifically /etc/pam.d/system-auth and /etc/pam.d/password-auth. Enabling TTY input auditing can support credential collection or keylogging-like behaviors by recording interactive terminal input. The detection relies on auditd telemetry capturing file path activity along with TTY/USER_TTY indicators.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1056.001/T1056.001.md
  - https://linux.die.net/man/8/pam_tty_audit
  - https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/security_guide/sec-configuring_pam_for_auditing
  - https://access.redhat.com/articles/4409591#audit-record-types-2
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/auditd/lnx_auditd_keylogging_with_pam_d.yml
author: Pawel Mazur, Huntrule Team
date: 2021-05-24
modified: 2022-12-18
tags:
  - attack.collection
  - attack.credential-access
  - attack.t1003
  - attack.t1056.001
logsource:
  product: linux
  service: auditd
detection:
  selection_path_events:
    type: PATH
    name:
      - /etc/pam.d/system-auth
      - /etc/pam.d/password-auth
  selection_tty_events:
    type:
      - TTY
      - USER_TTY
  condition: 1 of selection_*
falsepositives:
  - Administrative work
level: high
license: DRL-1.1
related:
  - id: 49aae26c-450e-448b-911d-b3c13d178dfc
    type: derived

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