BruteForceBlocker is a Perl script that works along with pf - OpenBSD's
firewall (which is also available on FreeBSD since version 5.2 is out).
Its main purpose is to block SSH bruteforce attacks via firewall.
When this script is running, it checks sshd logs from syslog and looks
for failed login attempts - mostly some annoying script attacks, and
counts number of such attempts. When given IP reaches configured limit
of fails, script puts this IP to the pf's table and blocks any further
traffic to the that box from given IP (this also depends on
configuration done in pf.conf).

WWW: http://danger.rulez.sk/index.php/bruteforceblocker/