Backtrack is a Linux distribution optimized for hackers or security people trying to stop them. It allows people to easily break into WEP and WPS enabled routers.
It’s alarmingly simple to crack a WEP account. That can be done in minutes. Most new routers have WPS enabled. That usually takes many hours to crack.
See this Lifehacker article on cracking WEP.
See this video from Skidhacker on cracking WPS.