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analyzing-persistence-mechanisms-in-linux

Inspect Linux scheduled tasks, services, shell profiles, shared library settings, and SSH keys for mechanisms that maintain attacker access. Correlate findings with audit logs to produce a timeline, risk scores, and remediation commands.

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Scan Linux systems for persistence mechanisms including crontab/systemd entries, LD_PRELOAD injection, shell profile modifications (.bashrc, .profile), and SSH authorized_keys backdoors, then correlate findings with auditd logs into an installation timeline. Use during incident response or threat hunting to detect or confirm how an adversary maintained access to a compromised Linux host.

See how to install

Good for

  • Investigating how attackers maintained access to a Linux host
  • Hunting for suspicious scheduled tasks and services
  • Building a timeline from persistence-related audit events
  • Checking monitoring coverage for persistence techniques

Files included (4)

  • SKILL.md3.1 KB
  • LICENSE11.0 KB
  • references/api-reference.md2.7 KB
  • scripts/agent.py10.2 KB

SKILL.md (original)

Review the instructions the agent will receive before you install.

Analyzing Persistence Mechanisms in Linux

Overview

Adversaries establish persistence on Linux systems through crontab jobs, systemd service/timer units, LD_PRELOAD library injection, shell profile modifications (.bashrc, .profile), SSH authorized_keys backdoors, and init script manipulation. This skill scans for all known persistence vectors, checks file timestamps and integrity, and correlates findings with auditd logs to build a timeline of persistence installation.

When to Use

  • When investigating security incidents that require analyzing persistence mechanisms in linux
  • When building detection rules or threat hunting queries for this domain
  • When SOC analysts need structured procedures for this analysis type
  • When validating security monitoring coverage for related attack techniques

Prerequisites

  • Root or sudo access on target Linux system (or forensic image)
  • auditd configured with file watch rules on persistence paths
  • Python 3.8+ with standard library (os, subprocess, json)
  • Optional: OSSEC/Wazuh agent for file integrity monitoring alerts

Steps

  1. Scan Crontab Entries — Enumerate all user crontabs, /etc/cron.d/, /etc/cron.daily/, and anacron jobs for suspicious commands
  2. Audit Systemd Units — Check /etc/systemd/system/ and ~/.config/systemd/user/ for non-package-managed service and timer units
  3. Detect LD_PRELOAD Hijacking — Check /etc/ld.so.preload and LD_PRELOAD environment variable for injected shared libraries
  4. Inspect Shell Profiles — Scan .bashrc, .bash_profile, .profile, /etc/profile.d/ for injected commands or reverse shells
  5. Check SSH Authorized Keys — Audit all authorized_keys files for unauthorized public keys with command restrictions
  6. Correlate Auditd Logs — Search auditd logs for file modification events on persistence paths to build an installation timeline
  7. Generate Persistence Report — Produce a risk-scored report of all discovered persistence mechanisms

Expected Output

  • JSON report of all persistence mechanisms found with risk scores
  • Timeline of persistence installation from auditd correlation
  • MITRE ATT&CK technique mapping (T1053, T1543, T1574, T1546)
  • Remediation commands for each detected persistence mechanism

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