A Daemon to Stop SSH Dictionary Attacks
This is a Linux daemon, written in C, that periodically monitors log files looking for multiple failed login attempts via the Secure Shell daemon (SSHD, or optionally, sshd2). The daemon is meant to mitigate what are 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 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.

The sshutout daemon 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. The sshutout daemon is merely one small tool intended to help reduce log clutter and diminish the incentive to mount dictionary attacks. you can free download sshutout 1.0.6 now.