SSHGuard protects hosts from brute-force attacks against SSH and
other services. It has been written entirely in C and has no external
dependencies and no configuration file. SSHGuard aggregates system
logs and blocks repeat offenders. It can read log messages from
standard input (suitable for piping from syslog) or monitor one or
more log files. Log messages are parsed, line-by-line, for recognized
patterns. If an attack, such as several login failures within a few
seconds, is detected, the offending IP is blocked. Offenders are
unblocked after a set interval, but can be semi-permanently banned
using the blacklist option.

IMPORTANT:

You will need to properly set up "sshguard" chain in iptables. For
further information PLEASE CONSULT MAN PAGE, installed together with
this package. The information available on the website tends to be
outdated, (it is well worth reading anyway).