Ninja Phone a badge of honor at Defcon 20 (photos)

The Ninja group has a reputation for doing some of the most innovative hacks at Defcon. This year they took to the airwaves and built a private cell phone network that runs only a custom flavor of Android called Ninja OS.From a corner of the vendor room at Defcon 20, a repurposed van sporting a "Ninja Tel" logo and a 12-foot cell phone tower broadcasts an GSM signal. It's available only to attendees lucky enough to score a Ninja Phone from the Ninja hacker group.

There's more than just a standard GSM network powering the Ninja Tel network. Ninja Tel uses a little-known feature of Android 4.0 Ice Cream Sandwich that allows networks to route calls over GSM or onto Wi-Fi, if the Wi-Fi has been configured properly using Session Initialization Protocol (SIP) and has a SIP Server. [Read more]