analyzing-linux-audit-logs-for-intrusion

name	analyzing-linux-audit-logs-for-intrusion
description	Use when using the Linux Audit framework (auditd) with ausearch and aureport utilities to detect intrusion attempts, unauthorized access, privilege escalation, and suspicious system activity. Covers audit rule configuration, log querying, timeline reconstruction, and integration with SIEM platforms. Activates for requests involving auditd analysis, Linux audit log investigation, ausearch queries, aureport summaries, or host-based intrusion detection on Linux.
domain	cybersecurity
tags	["auditd","ausearch","aureport","linux-security","intrusion-detection","HIDS","forensics"]
subdomain	incident-response
version	1.0.0
author	oyi77
license	Apache-2.0
nist_csf	["RS.MA-01","RS.MA-02","RS.AN-03","RC.RP-01"]

Analyzing Linux Audit Logs For Intrusion

Overview

Cybersecurity skill for analyzing linux audit logs for intrusion. Follows industry best practices and security standards.

When to Use

Trigger phrases:

• "analyzing linux audit logs for intrusion"

• "Uses the Linux Audit framework (auditd) with ausearch and aureport utilities to "

• Investigating suspected unauthorized access or privilege escalation on Linux hosts

• Hunting for evidence of exploitation, backdoor installation, or persistence mechanisms

• Auditing compliance with security baselines (CIS, STIG, PCI-DSS) that require system call monitoring

• Reconstructing a timeline of attacker actions during incident response

• Detecting file tampering on critical system files such as /etc/passwd, /etc/shadow, or SSH keys

Do not use for network-level intrusion detection; use Suricata or Zeek for network traffic analysis. Auditd operates at the kernel level on individual hosts.

When NOT to Use

• When you lack proper authorization for testing
• For production systems without change management
• When the task requires legal or compliance expertise beyond technical scope

Prerequisites

• Linux system with auditd package installed and the audit daemon running (systemctl status auditd)
• Root or sudo access to configure audit rules and query logs
• Audit rules deployed via /etc/audit/rules.d/*.rules or loaded with auditctl
• Recommended: Neo23x0/auditd ruleset from GitHub for comprehensive baseline coverage
• Familiarity with Linux syscalls (execve, open, connect, ptrace, etc.)
• Log storage with sufficient retention (default location: /var/log/audit/audit.log)

Workflow

# Example: IOC detection
import re

IOC_PATTERNS = {
    "ip": r"\b(?:\d{1,3}\.){3}\d{1,3}\b",
    "domain": r"\b[a-z0-9-]+\.[a-z]{2,}\b",
    : ,
    : ,
}

 () -> :
     {k: re.findall(v, text)  k, v  IOC_PATTERNS.items()}