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System Hardening: Secure Your System

System hardening secures your Linux system. Follow this checklist.

Here's the thing: Hardening reduces attack surface. Follow basics. You'll be more secure.

Hardening Checklist​

1. System Updates​

sudo apt update && sudo apt upgrade

# Enable automatic security updates
sudo apt install unattended-upgrades

My take: Updates fix security holes. Update regularly.

2. User Management​

# Disable root login
sudo passwd -l root

# Remove unused users
sudo userdel unused_user

# Set password policies
sudo chage -M 90 username

My take: Secure users. Remove unused accounts. Set policies.

3. SSH Hardening​

# /etc/ssh/sshd_config
PermitRootLogin no
PasswordAuthentication no          # Use keys only
Port 2222                          # Change default
MaxAuthTries 3

My take: Harden SSH. Disable root. Use keys. Change port.

4. Firewall​

sudo ufw enable
sudo ufw allow 22/tcp
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp

My take: Enable firewall. Block unwanted traffic.

5. Remove Unused Services​

# List services
systemctl list-units --type=service

# Stop and disable unused
sudo systemctl stop service-name
sudo systemctl disable service-name

My take: Remove unused services. Fewer services = smaller attack surface.

6. File Permissions​

# Set correct permissions
chmod 600 secret.txt
chmod 644 config.txt
chmod 755 script.sh

My take: Set permissions correctly. Don't use 777.

7. Monitoring​

# Monitor logs
journalctl -p err --since "1 hour ago"

# Check failed logins
grep "Failed password" /var/log/auth.log

My take: Monitor logs. Detect threats early.

Complete Checklist​

  • System updated
  • Root login disabled
  • SSH hardened
  • Firewall enabled
  • Unused services removed
  • Permissions set correctly
  • Logs monitored
  • Backups configured

My take: Follow this checklist. Your system will be more secure.

Common Mistakes (I've Made These)​

  1. Skipping updates: Updates fix security holes. Don't skip them.

  2. Using root for everything: Don't. Use sudo. Give minimum permissions.

  3. No firewall: Enable firewall. Block unwanted traffic.

  4. Weak passwords: Use strong passwords. Or better: SSH keys.

  5. Not monitoring: Monitor logs. Detect threats.

Real-World Examples​

Secure New System​

# Update
sudo apt update && sudo apt upgrade

# Harden SSH
sudo sed -i 's/PermitRootLogin yes/PermitRootLogin no/' /etc/ssh/sshd_config
sudo systemctl restart sshd

# Enable firewall
sudo ufw enable
sudo ufw allow 22/tcp

What's Next?​

Now that you understand hardening, your system is more secure. Or review what you've learned. You're ready.

Personal note: Hardening seemed tedious at first. Then I had a security incident. Now I harden everything. It's worth it. Follow the checklist.