Researchers at Georgia Tech and MIT have developed a proof of concept to demonstrate that it is possible to record a computer user's keystrokes using an iPhone 4's accelerometer. The researchers developed a method to accurately translate the vibrations from typing on a keyboard picked up by the device's accelerometer when placed on a desk near a PC. Though they warn that hackers could potentially use their method to eavesdrop on a user's keystrokes, they believe the actual threat is quite low.
The method, detailed in a paper titled “(sp)iPhone: Decoding Vibrations From Nearby Keyboards Using Mobile Phone Accelerometers,” works by interpreting pairs of keystrokes in successive order. According to principal researcher Patrick Traynor, assistant professor at Georgia Tech’s School of Computer Science, the method can't reliably pinpoint single keystrokes. But by characterizing the successive strokes as left-right, right-left, left-left, or right-right, and then whether the pair is nearer or further away form the device, the pairs can be statistically analyzed to represent probably letter pairs. Then those pairs can be compared to a dictionary.