You should check out the website of Oxid for their freeware tool called “Cain & Abel“. It is a password recovery tool that does a variety of hacking (brute force, dictionary, and others) plus decoding/decrypting, sniffing and loads more. It really makes you think about security from the perspective of the hacker. Look and learn.
From the documentation:
“Cain & Abel is a password recovery tool for Microsoft Operating Systems. It allows easy recovery of various kind of passwords by sniffing the network, cracking encrypted passwords using Dictionary, Brute-Force and Cryptanalysis attacks, recording VoIP conversations, decoding scrambled passwords, revealing password boxes and analyzing routing protocols.”