Why I Always Restrict Cron Jobs on Linux Servers | by Faruk Ahmed | Sep, 2025

Member-only story

Why I Always Restrict Cron Jobs on Linux Servers

--

Share

Cron is one of the most powerful features in Linux — it automates tasks, rotates logs, and runs maintenance scripts. But in my experience, cron is also one of the easiest places for attackers to hide persistence .

That’s why I always restrict, monitor, and audit cron jobs as part of my hardening process.

🚨 Why Cron Jobs Can Be Dangerous

• Persistence Backdoor Attackers drop malicious scripts in /etc/cron.d/ or user crontabs to execute silently. /etc/cron.d/ - Privilege Abuse If cron runs as root, even a simple script ( wget a payload, start a reverse shell) can compromise the system. wget - Silent Failures A cron job can fail quietly without alerting you, while malicious jobs keep running unnoticed.

🔍 Step 1: List All Cron Jobs

System-wide:

ls -la /etc/cron* cat /etc/crontab

Per user:

crontab -l -u username

Systemd timers (often overlooked):

systemctl list-timers --all

🛠 Step 2: Restrict Cron Access

Edit:

vi /etc/cron.allow vi /etc/cron.deny

---

👉 Read Full Blog on Medium Here