Today I couldn't remember some software I used 14 years ago to block IP addresses that are attacking your server in a denial of service (DoS) attack. I emailed a colleague and friend who was on the same team with me back then and he replied right away. Awesome.

It turns out I did remember the software that he still uses, which is called fail2ban. The one I forgot is called DenyHosts, which he no longer uses.

He also sent me some helpful commands from his wiki:

To view a list of IP's that are in jail, run:

iptables -L -n

To check the status of Fail2ban, run:

fail2ban-client status

To unblock an IP address, run:

fail2ban-client set ssh-iptables unbanip [XX.XX.XX.XX]