Linux Log Analysis – Turning Noise Into Action

by

The Problem

A Linux server generates thousands of log lines per hour. Without structure, critical alerts drown in noise. Attackers rely on this.

Core Logs to Monitor

  1. /var/log/auth.log – SSH, sudo, login attempts.
  2. /var/log/syslog / messages – system and kernel alerts.
  3. journald – structured logging with filters.
  4. Application logs – Apache, Nginx, PostgreSQL, etc.

Practical Analysis Tools

  • journalctl: filtering by user, service, or time window.
  • ausearch: auditd-based forensic digging.
  • logwatch/logcheck: daily digest reports.
  • grep + awk pipelines: still powerful for ad hoc triage.

Applied Example

journalctl _COMM=sshd --since "1 hour ago"

→ flags suspicious repeated SSH attempts in real time. Pair with Wazuh for automatic escalation.

Why Clients Care

  • Faster incident response.
  • Lower SOC fatigue from false positives.
  • Direct tie-in to ISO 27001 logging requirements.