Your phone's power usage can reveal where you've been

When you think of smartphone location tracking, both legitimate or otherwise, and you will most likely think of technologies that directly relate to locations, like GPS, WiFi, or even Bluetooth. But a group of researchers from Standford University and Israeli defense group Rafael are proving even something so innocent sounding like your phone's battery consumption can be used to track your movements. The good news is that it's not exactly as easy or as informational as those more dedicated sensors. At least not yet.

The researchers are calling this technique as "PowerSpy", and the name fits considering it can be used to spy on you. It works on the basis that your device consumes more power when it travels farther away from a cell tower it was connected to. It also uses up energy when trying to overcome obstacles like buildings and such. By observing a device's power usage over time and correlating it with the landscape and cell tower distances, the researchers are able to trace the smartphone's movements with 90 percent accuracy, even taking into account sudden spikes in battery usage like from a phone call or a game.

The catch is that PowerSpy isn't yet as exact or as reliable as the harder but more direct route of getting information from GPS. For one, the layout of the area where the targeted smartphone is expected to travel must already be known before hand. Even more difficult is the requirement that spies already pre-calculate the possible routes and power usage data yielded by those routes. In other words, they must already have a standard to measure against before they can determine that this is indeed the route taken by a smartphone user.

The one advantage that PowerSpy has over other methods is the ease of deceiving users. Most mobile platforms, particularly Android, inform users that an app will access GPS information, which may make it harder to fool users into installing malicious apps. Accessing battery information, on the other hand, is so boring that the platform simply gives every app permission.

The researchers aren't done yet either. Aside from trying to improve the overall accuracy of the method, they are also trying out other things, like detecting the device's location faster in real-time or accurately determining a phone's location even if taking a route not previously calculated. There's also the factor of power consumption "noise" coming from too many apps using the battery at the same time. Hopefully, Google will become aware of this possible security hole and implement stricter rules for which apps can access that kind of information.