Your mobile phone can give away your location, even if you tell it not to

U.S. military officials were recently caught off guard by revelations that servicemembers’ digital fitness trackers were storing the locations of their workouts — including at or near military bases and clandestine sites around the world. Apps on the phone can use those sensors to perform tasks users aren’t expecting — like following a user’s movements turn by turn along city streets. In one recent project, we developed an app that could determine what letters a user was typing on a mobile phone’s on-screen keyboard — without reading inputs from the keyboard. Identifying a location We then wondered whether a malicious application could infer a user’s whereabouts, including where they lived and worked, and what routes they traveled — information most people consider very private. That app also used the phone’s gyroscope, measuring the sequence of turn angles of the route traveled by the user.