“It takes a thief to catch a thief”
In the computing security sense, it means that crackers are the most knowledgeable about security flaws. Here is some information I have gleamed:
Hack #1: The Double-router
A router is set up with the same SSID as the sought-for network. The router is set so that if someone enters a WEP, WPA, or WPA2 key. it automatically sends it along to teh main router and acts as a proxy of sorts. This gives the of the “fake” router the key. This only works if the user clicks on one of the networks randomly and gets the “fake” one.