This Is Your Brain On Informatics: DenyHosts
DenyHosts is a firewall that is built for the Linux OS and is probably the easiest way to secure a server. This program prevents unauthorized access to the server by blocking an IP address after a set number of unsuccessful attempts have been made.
Installing DenyHosts
Currently, as of writing this wiki page (12/01/13), the easiest way to install DenyHosts is to use aptitude by typing in the following command.
aptitude install denyhosts
Important Files
There are two important files in DenyHosts in order to make sure that it runs properly. The location of both of these files can be found in common pathnames.