IP address unban

Fail2Ban is an intrusion prevention system that protects computer servers from brute-force attacks. It can monitor specific logs and block IP addresses that act like brute-force attacks.

Fail2Ban particularly monitors the number of connection attempts. After 5 failed SSH connection attempts, Fail2Ban will ban the IP address from connecting via SSH for 10 minutes. If this address fails several times, it might be banned permanently until you contact admin@richardapplegate.io and explain why you are attacking my server.

Unban an IP address

To unblock an IP address, you must first access it from another IP (VPN) address or internet connection than the one that is blocked.

Look at the Fail2Ban log to find out where the IP address was banned.jail

sudo tail /var/log/fail2ban.log 
2019-01-07 16:24:47 fail2ban.filter  [1837]: INFO    [sshd] Found 11.22.33.44 
2019-01-07 16:24:49 fail2ban.filter  [1837]: INFO    [sshd] Found 11.22.33.44 
2019-01-07 16:24:51 fail2ban.filter  [1837]: INFO    [sshd] Found 11.22.33.44 
2019-01-07 16:24:54 fail2ban.filter  [1837]: INFO    [sshd] Found 11.22.33.44 
2019-01-07 16:24:57 fail2ban.filter  [1837]: INFO    [sshd] Found 11.22.33.44 
2019-01-07 16:24:57 fail2ban.actions [1837]: NOTICE  [sshd] Ban 11.22.33.44 
2019-01-07 16:24:57 fail2ban.filter  [1837]: NOTICE  [recidive] Ban 11.22.33.44

Here, the 11.22.33.44 IP address has been banned in the sshd and recidive jails.

Then use the following commands to unban the IP address.

sudo fail2ban-client set sshd unbanip 11.22.33.44
sudo fail2ban-client set recidive unbanip 11.22.33.44