In spy movies, the way both good guys and bad guys often ditch pursuers is by hopping on a subway or metro. It's an easy way to lose yourself in a large crowd, and still be on the move. And if you're in a subway, it's harder for someone to track your GPS location.
Now researchers have made the surprising discovery that riding a subway can actually make you a better target to track. And it's actually easier than GPS tracking or cell tower triangulation.
The researchers, out of Nanjing University, used an app to record accelerometer sensor data on volunteers' phones. Because metro lines have set lengths and scheduled stops, matching up the sensor data with where the person had traveled turned out to be easy.
Depending on how far the person traveled, the researchers could track their movements with 70% to 92% accuracy. A hacker, or government, who had an app like this running for days or weeks could quickly build up a database of your movements. And if this type of app was running on the phones or thousands or millions of people, someone could figure out who was meeting up with who, who worked together, etc.
The really scary part, however, is that creating a tracking app like this is no big deal. Apps, particularly on Android smartphones and tablets, are allowed to access gadget sensor data without needing permission, unlike GPS location. Any app you download could be recording data from your gadget's sensors.
Even worse, you'd probably never know you were being tracked. The researchers say the only sign would be increased battery use, although it wouldn't be much. You might also throw off the tracking by moving your phone around a lot. Any other defense against this would have to come from the phone manufacturer's side.
Are you worried about this development in tracking? Let me know your thoughts in the comments below.