Your Phone’s Gyroscope Is the Next Threat to Your Privacy

Another day, another potential invasion of our collective privacy.

By now, most of us are either savvy enough or paranoid enough to restrict access to our phones’ hardware. We know to tap Do Not Allow when that new shopping app asks for access to our camera or microphone. It’s a no-brainer. But where there’s a will there’s a way, and attention is now turning to another integral part of your phone: the gyroscope. The kicker is that the app in question won’t even need to ask for your permission.

In an upcoming presentation at the USENIX Security Conference, a team of researchers from Stanford University and an Israeli research group called Rafael will present their findings on how to hijack a smartphone’s gyroscope and use it to eavesdrop on nearby conversations. In other words, what used to be a mostly benign piece of hardware used for simple tasks like motion-based gameplay and fitness tracking can now be used to spy on the phone’s owner.

If you build it, they will use it to spy on you.

One of the Stanford-based members of the team, Dan Boneh, had this to say: “Whenever you grant anyone access to sensors on a device, you’re going to have unintended consequences… In this case, the unintended consequence is that they can pick up not just phone vibrations, but air vibrations.”

To be fair, the team’s method is far from perfect – and that’s a good thing; our phones are already plenty capable of being used against us. For now, using a phone’s gyroscope for surveillance purposes is more of a gimmick than an actual practical solution; only a rather small fraction of the words being spoken will be picked up by the device. While the method was being tested, researchers found that their gyroscopes correctly identified only about 65% of what was being said. More interestingly, it could correctly guess the speaker’s gender about 84% of the time.

For right now, this method serves as little more than a proof of concept – or, if you prefer, a proof of threat. Simply demonstrating that this can be done, even if it’s far from a perfect “solution,” should serve as a warning not only to smartphone owners, but also to companies like Apple and Google, whose app creation guidelines are largely responsible for governing access to certain parts of their phones’ hardware. Right now, apps are required to ask users’ permission before accessing the camera or microphone, for example, and that list will likely soon include the gyroscope as well.

Said Boneh: “It’s actually quite dangerous to give direct access to the hardware like this without mitigating it in some way… The  point is that there’s acoustic information being leaked to the gyroscope. If we spent a year to build optimal speech recognizion, we could get a lot better at this. But the point is made.”

Yes, it has been.

Most gyroscope-equipped smartphones work on the same principle: they use a tiny vibrating plate affixed to a microchip. Any time the phone’s orientation is changed, the plate is moved around by the Coriolis forces.

But the lynchpin of the group’s research was finding out that physical vibrations aren’t the only thing the gyroscope can pick up; it can also detect vibrations in the air, albeit imperfectly. Android phones, for example, allow gyroscopes to pick up on movements at 200 hertz (200 times every second). Human voices tend to range from 80 to 250 hertz, making them prime targets.

Previous research has found similar exploits for smartphone gyroscopes, including their ability to register keystrokes on nearby computers.

But here’s the bottom line for smartphone owners: there’s rather little to worry about. Apple already restricts the frequency with which an app may access the iPhone’s gyroscope, and with a simple software tweak, Google could follow suit.

Right now let’s all just appreciate the fact that the good guys were the first ones to discover this exploit.

Image Credit: Misko (via Flickr)

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