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Linux Administration · Module 8 of 10

Security and firewalls

Harden Linux servers.

📖 Key ideas

  1. Use SSH keys; disable password login and root login.
  2. Firewalls: ufw (Ubuntu), firewalld (RHEL).
  3. fail2ban blocks repeated failed logins.
  4. Keep packages updated; remove unused services.
  5. SELinux/AppArmor add mandatory access controls.
💡 Real-life example: Server hardening is locking every door and window except the one you actually use.
ufwUncomplicated Firewall
fail2banBans IPs after failed logins
SSH keyKey-based authentication
SELinuxMandatory access control system