Smartphone battery consumption is enough to track your geo-location, say researchers

Researchers from Stanford University discover that Android phones can be tracked without the use of GPS or Wi-Fi data by studying their power usage over time. Yan Michalevsky, Dan Boney, Aaron Schulman of the Computer Science Department at Stanford University have created an algorithm that monitors smartphones’ power consumption in relation to their distance from a cellular base, while carefully factoring out power used by other apps and functions running in the background. 

“The malicious app has neither permission to access the GPS nor other location providers (eg cellular or wi-fi network),” wrote the team in their paper. Instead, the app they’ve created takes into account the fact that phones use more power the further they are from a cellular base, and the more obstacles are in they of the signal’s path.

The team explains that their technique is completely legal; power consumption data is considered harmless and current laws dictate that acquiring said data doesn’t require user permission or notification. “We only assume permission for network connectivity and access to the power data. These are very common permissions for an application, and are unlikely to raise suspicion on the part of the victim.” There are currently 179 Android apps on Google Play that request this information.

The main takeaway here is that every action — web browsing, listening to music, opening apps, social media, and taking calls — drains battery life and produces noisy, aggregated data that’s difficult to distinguish, but the team has managed to “use machine learning” to automate the process of data filtering using a proprietary algorithm. “Intuitively the reason why all this noise does not mislead our algorithms is that the noise is not correlated with the phone's location,” says the report, “therefore a sufficiently long power measurement (several minutes) enables the learning algorithm to 'see' through the noise,” and infer the user’s location.

The tests were conducted on phones using the 3G network, and did not measure signal strength, as this information is protected. What these findings demonstrate, is the even rudimentary data has the potential to invade users’ privacy is properly recorded.

Source: Stanford University