Linux Server Hardening: Essential Security Checklist

Why Server Hardening Matters

Every Linux server exposed to the internet is a potential target. Server hardening reduces the attack surface and minimizes vulnerabilities. Here's a practical checklist to get you started.

1. Keep Your System Updated

Always run the latest security patches:

# Debian/Ubuntu
sudo apt update && sudo apt upgrade -y

# RHEL/CentOS
sudo dnf update -y

2. Configure SSH Securely

SSH is the primary access point — lock it down:

• Disable root login: PermitRootLogin no
• Use key-based authentication instead of passwords
• Change the default port (optional but adds a layer)
• Limit SSH access to specific users: AllowUsers yourusername

3. Set Up a Firewall

Use ufw or firewalld to restrict traffic:

# UFW example
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw allow http
sudo ufw allow https
sudo ufw enable

4. Disable Unused Services

Check what's running and disable what you don't need:

systemctl list-units --type=service --state=running
sudo systemctl disable --now unnecessary-service

5. Implement Fail2Ban

Protect against brute-force attacks:

sudo apt install fail2ban
sudo systemctl enable --now fail2ban

6. Regular Auditing

• Review logs regularly (/var/log/auth.log, /var/log/syslog)
• Use tools like lynis for automated security audits
• Set up log monitoring and alerting

Conclusion

Server hardening is not a one-time task — it's an ongoing process. Start with these fundamentals and build upon them as your infrastructure grows.

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