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Event: auth_logs_tamper

Quick Explanation

The auth_logs_tamper detection recipe detects suspicious file operations—specifically the removal or truncation of critical system authentication logs. These actions can signal attempts to hide activity or evade detection mechanisms, exposing the environment to stealthy intrusions or breaches if left unchecked.

More Information

Information

  1. Description: Authentication logs tampering
  2. Category: Defense Evasion
  3. Method: Indicator Removal on Host
  4. Importance: High

Analysis of the Event

The detection event, identified by Jibril as auth_logs_tamper, triggers on file removal (unlink) or truncation operations performed on key authentication and logging files. Attackers often target these logs (e.g., secure, wtmp, btmp) to erase traces of malicious activity, making it more difficult for defenders to piece together timelines or detect intrusions.

From a MITRE perspective, this aligns with techniques where adversaries remove indicators on a host to obscure their presence. Log tampering in a CI/CD context is particularly dangerous because it can hide unauthorized changes or malicious code introduced during the build process. By eliminating or corrupting evidence, adversaries can remain undetected and potentially persist within systems or applications.

At a deeper level, removing or truncating authentication logs can invalidate a critical forensics data source, hamper incident investigation efforts, and disrupt normal auditing procedures. This tactic can be combined with other methods of lateral movement or privilege escalation to quietly expand an attacker’s foothold within the environment.

Implications for the CI/CD Pipeline

In the context of a CI/CD pipeline, the ability to remove or erase system authentication logs indicates a highly concerning security regression. If such a change is merged, malicious actors could tamper with logs during build or deployment stages, concealing unauthorized alterations. This behavior threatens both the integrity of the build process and the production environment, where attackers could stealthily gain access, escalate privileges, and disrupt normal operations without leaving reliable audit trails.

  1. Review Recent Changes: Inspect the pull request and associated commits for code paths enabling file removal or truncation of authentication logs. Identify any newly introduced commands, scripts, or dependencies capable of performing these operations.

  2. Validate Permissions: Ensure strict file permissions and access controls are enforced on critical log files. Restrict or monitor processes that can unlink or truncate these files.

  3. Augment Monitoring: Deploy additional logging and alert mechanisms for system and authentication logs. Watch specifically for any repeated file operations against /var/log and associated directories.

  4. Conduct Security Assessments: Run targeted security scans or penetration tests on the modified code and surrounding infrastructure to detect any hidden tampering capabilities.

  5. Implement Tamper-Proofing Measures: Where feasible, consider using append-only file systems or centralized logging solutions that automatically collect and store logs off-host, complicating efforts to remove or hide them.

  6. Educate Teams: Brief developers and DevOps staff on the criticality of logs in post-incident forensics and why changes that remove or truncate logs pose a security risk.

By following these steps, teams can mitigate the immediate risks associated with this detection and establish a more resilient security posture for future releases and deployments.