Researchers try to eavesdrop on smartphones via gyroscope

American and Israeli researchers have managed to record sounds from a smartphone by measuring the vibrations of the gyroscope. The trick only works on Android devices but is not yet precise enough to be a threat to privacy.

Applications are allowed to read the gyroscope in a device without permission, so that any app can detect the vibrations. Despite this, it is not yet a privacy threat due to the inaccuracy of the technology, Wired writes.

The technology works because gyroscopes in smartphones are vibration gyroscopes: they detect movement because an element in the gyroscope constantly vibrates and keeps moving on the same axis when it rotates. The researchers say the gyroscope picks up vibrations from the human voice; reading out those vibrations is therefore theoretically enough to pick up the words, as if the gyroscope were a microphone.

The problem is that the technology is currently still too imprecise: in a test, for example, it did not pick up two-thirds of the digits in a series of numbers correctly, making it difficult, for example, to tap a credit card number. The trick only works on Androids, because Google’s mobile operating system allows reading the gyroscope at 200Hz, close to the maximum 250Hz of the human voice. With iOS that is limited to 100Hz, so eavesdropping would not be possible.

The researchers from the American Stanford University and an Israeli company say they can still tinker with the technology to improve word recognition. Google could anticipate the possible privacy problem that would then arise by making the reading of the gyroscope a permission; currently apps don’t need permission for that. Gyroscopes are in many modern smartphones.

Close-up of the gyroscope in an iPhone, made by ST Microelectronics. Photo: Chipworks