thc-hydra
Shows how easy it would be to gain unauthorized access to a system
...There are already several login hacker tools available, however, none does either support more than one protocol to attack or support parallelized connects. It was tested to compile cleanly on Linux, Windows/Cygwin, Solaris, FreeBSD/OpenBSD, QNX (Blackberry 10) and MacOS. However the module engine for new services is very easy so it won't take a long time until even more services are supported. Via the command line options you specify which logins to try, which passwords, if SSL should be used, how many parallel tasks to use for attacking, etc. ...