This is Alec Muffett's Crack.

Crack is a freely available program designed to find encrypted passwords. 

When you would like to crack a 4.4BSD password file:

	Crack -fmt bsd <password_file>

Or, for non-BSD machines:

	Crack <password_file>

WWW: http://www.crypticide.com/alecm/security/c50-faq.html