How the NSA can 'turn on' your phone remotely

Even if you power off your cell phone, the US government can turn it back on. That's what ex-spy Edward Snowden revealed in a recent interview with NBC's Brian Williams.

It sounds like sorcery. Can someone truly bring your phone back to life without touching it? No. But government spies can get your phone to play dead.

It's a crafty hack. You press the button. The device buzzes. You see the usual power-off animation. The screen goes black. But it'll secretly stay on -- microphone listening and camera recording.

How did they get into your phone in the first place? Here's an explanation by former members of the CIA, Navy SEALs and consultants to the US military's cyber warfare team. They've seen it firsthand.

Government spies can set up their own miniature cell network tower. Your phone automatically connects to it. Now, that tower's radio waves send a command to your phone's antennae: the baseband chip. That tells your phone to fake any shutdown and stay on. A smart hack won't keep your phone running at 100%, though. Spies could keep your phone on standby and just use the microphone -- or send pings announcing your location.

John Pirc, who did cybersecurity research at the CIA, said these methods -- and others, like physically bugging devices -- let the US hijack and reawaken terrorists' phones. "The only way you can tell is if your phone feels warm when it's turned off. That means the baseband processor is still running," said Pirc, now chief technology officer of the NSS Labs security research firm.