iplock

The iplock tool is a simple iptables extension that allows you to run iptables commands that otherwise require root access in order to block and unblock IP addresses in your firewall.

This is particularly useful if you have a webserver such as Apache2 running a scripting language such as PHP without root permissions. When you detect that a user is likely a hacker (i.e. tries to access a folder named wp-admin on a non-Wordpress website) then you can use iplock <his-IP-address> to block him.

The iptables commands are defined in the configuration file so you can really tweak your firewall to your liking.