It is Automatic Black-List with PAM module, which can help you to protect SSH server.
I have Centos 5.5 linux server on Butstnet.
From log file, I saw a lot of fail login on my SSH server every day.
To save the resource and block them, I google and got the idea to install PAM-abl to stop them.
I just noted here for my experience.
1) install pam devel package