"My password is stronger than your password!"

"Oh, yea... Prove it!"
...even strong passwords can be cracked in seconds using an open source tool called Ophcrack.

Ophcrack is an extremely fast password cracker because it uses a special algorithm called rainbow tables. Brute-force cracking tools typically try thousands of combinations of letters, numbers and special characters each second, but cracking a password by attempting every conceivable combination can take hours or days. (by Scott Sidel)