Hearing your touch: A new acoustic side channel on smartphones

Understand

We present the first acoustic side-channel attack that recovers what users type on the virtual keyboard of their touch-screen smartphone or tablet.

• When a user taps the screen with a finger, the tap generates a sound wave that propagates on the screen surface and in the air.
• We found the device's microphone(s) can recover this wave and "hear" the finger's touch, and the wave's distortions are characteristic of the tap's location on the screen.
• Hence, by recording audio through the built-in microphone(s), a malicious app can infer text as the user enters it on their device.