Sensors Tap Into Mobile Vibrations to Eavesdrop Remotely

Using an off-the-shelf automotive radar sensor and a novel processing approach, Penn State researchers demonstrated they could detect the vibrations of a cell phone's earpiece and decipher what the person on the other side of the call was saying with up to 83% accuracy...

The radar operates in the millimeter-wave (mmWave) spectrum, specifically in the bands of 60 to 64 gigahertz and 77 to 81 gigahertz, which inspired the researchers to name their approach "mmSpy." This is a subset of the radio spectrum used for 5G, the fifth-generation standard for communication systems across the globe.

In the mmSpy demonstration, the researchers simulated people speaking through the earpiece of a smartphone. The brand is irrelevant, Basak said, but the researchers tested their approach on both a Google Pixel 4a and a Samsung Galaxy S20. The phone's earpiece vibrates from the speech, and that vibration permeates across the body of the phone.

"We use the radar to sense this vibration and reconstruct what was said by the person on the other side of the line," Basak said, noting that their approach works even when the audio is completely inaudible to both humans and microphones nearby. more

This paper presents a system mmSpy that shows the feasibility of eavesdropping phone calls remotely. Towards this end, mmSpy performs sensing of earpiece vibrations using an off-the-shelf radar device that operates in the mmWave spectrum (77GHz, and 60GHz). abstract