Intermediate5 lessons130 minutes
Firewall and hardening
Close what has no business being open, slow automated attacks down, and check regularly what the server exposes — without locking yourself out.
A server on the internet receives connection attempts continuously. This course reduces the attack surface with ufw and fail2ban, then sets up the periodic verification that matters more than the initial installation.
What you will be able to do
- Configure ufw as default-deny without losing your SSH access
- Understand why Docker bypasses ufw, and what that means
- Ban repeated attempts with fail2ban, and unban yourself
- Know what a server actually exposes, and check it periodically
Outline
- 01
The firewall
Deny by default, allow deliberately — and do not saw off the branch.
- 02
Knowing what the machine exposes
The periodic check, which matters more than the initial configuration.
Technical content last reviewed on 3 August 2026