DenyHosts is a script intended to be run by system administrators
to help thwart SSH server attacks (also known as dictionary based
attacks and brute force attacks).

In short, it does this by monitoring your syslog output for failed
login attempts and tweaking /etc/hosts.deny accordingly, and it can
optionally send and fetch lists of ssh probers from a central server.

Homepage:
https://denyhosts.sourceforge.net/
