sshtrix is a very fast multithreaded SSH login cracker. It supports SSHv1 and SSHv2.sshtrix was designed to automate rapid bruteforce attacks against SSH authentification screens. Unlike other public tools, the aim is to keep it simple, stable, fast and modular. With its clean code design, it is easy to extend the code to a framework or to fork it against protocols of your choice. In fact, sshtrix is a fork of my own generic login cracker framework.
Download SSHtrix here