authfail is a tool for adding IP addresses to an ACL when entities from those addresses attempt to log into a system, but cause authentication failures in auth.log. It reads data from auth.log in real time and adds the IP into netfilter with a DROP/REJECT policy.
You can download it from the following link: https://packetstormsecurity.com/files/download/37120/authfail-1.1.2.tgz
Source: https://packetstormsecurity.com/files/37120/authfail-1.1.2.tgz.html

