thc-hydra
Shows how easy it would be to gain unauthorized access to a system
Number one of the biggest security holes are passwords, as every password security study shows. This tool is a proof of concept code, to give researchers and security consultants the possibility to show how easy it would be to gain unauthorized access from remote 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.