Fail2Ban is an intrusion prevention software framework that protects computer servers from brute-force attacks.

Source: https://en.wikipedia.org/wiki/Fail2ban

Fail2ban detects repeated failed logins, and bans the IP address. Subsequent attempt to establish SSH connection from this IP will be blocked. It is available as package in most Linux distro repositories. It works out of the box without configuration. I highly recommend installing it in all Linux servers.

Common Usage

Unban an IP address

sudo fail2ban-client set sshd unbanip 123.123.123.123

List jail names

sudo fail2ban-client status

List blacklisted IP addresses for SSHD

sudo fail2ban-client status sshd