While checking one of my servers a few days ago, I discovered a lot of failed SSH logins from several remote servers. Right away, I checked to see if my server was compromised and I was glad to know that it wasn’t. Whew! 
So as to protect myself to further brute force attacks, I decided to install DenyHosts. It’s a simple python application that monitors your auth.log/secure.log for any login attempts and failures, and then adds the hosts that has registered a number of failed logins on your hosts.deny file. The number of failed login attempts is configurable for root and normal users before the IP source would be refused connection. Moreover, you can always purge the blocked hosts depending on your preference (e.g. 1 week, 1 month, etc.). It may never give me a 100% security breach protection for my server, but at least and additional layer of protection would definitely help. At least this would discourage brute force attackers from targeting your server and also save you some resources on login attempts. As the saying goes, “An ounce of prevention is worth a pound of cure”. 
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