"New “Glowworm attack” recovers audio from devices’ power LEDs"

Clever study showing a new way to spy on electronic audio signals:

A new paper released today outlines a novel passive form of the TEMPEST attack called Glowworm, which converts minute fluctuations in the intensity of power LEDs on speakers and USB hubs back into the audio signals that caused those fluctuations.

(Emphasis mine.) The attack is limited by line-of-sight of course, but the study showed that intelligible sound could be recovered at up to 35 meters.

Reminds me of the study showing you can identify what a TV is playing by measuring current fluctuations in the TV’s power draw. Also similar to the idea of laser microphones that could listen to conversations in a room with a window by measuring small deflections in the window due to sound waves.

https://arstechnica.com/gadgets/2021/08/new-glowworm-attack-recovers-audio-from-devices-power-leds/