sshutout periodically monitors log files looking for multiple failed login attempts
via the sshd (optionally, sshd2). It is meant to mitigate what is commonly
known as "dictionary attacks," i.e. scripted brute force attacks that use lists
of user IDs and passwords to effect unauthorized intrusions. Typically such
attacks fill up the system logs with hundreds or even thousands of log entries
for the failed login attempts. Aside from the nuisance of wasted space, wasted
bandwidth, and reduced signal to noise ratio in the logs, the attacks can pose
a real danger to systems with weak ID and password combinations.

This package blunts such attacks by creating firewall rules to block individual
offenders from accessing the system. These rules are created when an attack
signature is detected, and after a configurable expiry interval has elapsed,
the rules are deleted.

While sshutout can help reduce the severity and impact of dictionary attacks,
it is by no means a substitute for a good password policy. A password policy
is the front line of defense against intrusion and should be given careful
consideration. sshutout is merely one small tool intended to help reduce log
clutter and diminish the incentive to mount dictionary attacks.

• Michael Shigorin

• sshutout