DenyHosts
An excellent tool in the fight against brute force SSH server hackers. Simple to setup, simple to use, and highly effective against the majority of password cracking attempts on your SSH server.
DenyHosts is a script intended to be run by Linux system administrators to help thwart SSH server attacks (also known as dictionary based attacks and brute force attacks).
http://denyhosts.sourceforge.net/
Preventing SSH Dictionary Attacks With DenyHosts
How to set DenyHosts up on a Debian based system. This applies to Ubuntu and Kubuntu families too.
http://www.howtoforge.com/...ith_denyhosts
