How to Audit Your Linux Server for Hidden Threats in Under 15 Minutes

🧠 Blog Outline:

Intro:

Think your server is secure? Even hardened Linux boxes can hide overlooked risks — unused services, rogue cron jobs, outdated packages, or config leaks. This 15-minute audit is something I run on every Ubuntu and Red Hat server I manage. You don’t need fancy tools — just your terminal and focus.

1. Check for Suspicious Active Users

who
lastlog

Look for:

• Accounts that haven’t logged in for months
• Unexpected active sessions

2. Review Sudoers and Privileged Access

cat /etc/sudoers
getent group sudo    # Ubuntu
getent group wheel   # Red Hat

✅ Action: Remove users who shouldn’t have elevated access.

3. Scan Running Services

ss -tuln
ps aux --sort=-%mem | head

✅ Action:

• Stop unused services
• Investigate unfamiliar processes

4. Inspect Scheduled Tasks

crontab -l
ls /etc/cron.* /var/spool/cron/