Lifehacker wrote a guide for cracking a WiFi network’s WEP password using BackTrack. BackTrack is a Linux live CD used for security testing and comes with the tools needed to break WEP. Not just any wireless card will work for this; you need one that supports packet injection. The crack works by collecting legitimate packets then replaying them several times in order to generate data. They point out that this method can be hit-or-miss, especially if there are few other users on the network, as the crack requires authenticated packets. We covered cracking WEP before, but using BackTrack should smooth out compatibility issues.