Spies and cops can use your smartphone to track your movements. That's no mystery—most smartphones come with a GPS chip that makes it pretty damned simple. So if you don't want to be tracked, you just turn off the GPS feature, right? Unfortunately, there is another way prying eyes can follow your movements: through your Android phone's battery.


A team of security researchers from Stanford and the Israeli government just published the details of a technique that lets spies watch you as you move around by monitoring tiny changes in your phone's battery levels. It all comes down to how hard your phone has to work to ping cell towers. The towers that are further away or obscured by a building or hill cause your phone to use a little bit more power. So if—and this is a big "if"—the spies know your normal routine, they can track your movements with 90 percent accuracy. If they don't know your routine, that accuracy drops to about 60 percent.

This is especially concerning because there's not really any way to protect yourself from this kind of surveillance, aside from taking out your phone's battery. Google lets pretty much any app gain access to battery usage data, so a hacker could either build a fake app to monitor that data or pull data from another app.


Click over to Wired for more details on this new battery-hawking surveillance technique. You can also read the Stanford-Israel study in full below.