Ars Technica writes, The Ninja Tel van housing a fully functional GSM network at the Defcon hacker conference in Las Vegas. Dan Goodin The WiFi at the annual Defcon hacker conference has long been inhabited by a battery of live and automated mischief makers that sniff packets, scan ports, and exploit whatever weaknesses can be found. Last year, cellular networks were also rumored to be compromised, raising the question: How does one stay both safe and connected at the Las Vegas-based confab? For a hacker crew known as Ninja Networks, the answer was to build its own private phone network, complete with 650 HTC One...