Your webcam’s microphone can reveal what’s on your screen during video calls

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Ever enjoy a sneaky spot of online shopping during conference calls, or plan a vacation while chatting with your manager? It might be time to stop. Security researchers have demonstrated a way to find out what’s being displayed on another person’s screen during a video call using only the audio from their webcam.

The researchers published their findings at last week’s CRYPTO 2018 conference in Santa Barbara, according to Ars Technica. The method, named Synesthesia, uses ‘coil whine’ – a barely audible sound emitted by an LCD monitor as it’s refreshed.

The whine can not only be captured by a webcam during video conferences – it can also be recorded by a nearby smart speaker, a smartphone, or a cheap USB microphone.

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The researchers taught a neural network to recognize ultrasonic sounds associated with particular patterns on a monitor. After training, the system was able to identify which of the 10 most popular websites was displayed on-screen with 96.4% accuracy.

Synthesia is a novel way to breach security using data that would normally go ignored – much like the creative Thermonator hack demonstrated last month, which allows would-be crooks to discover passwords using residual heat on recently pressed keys.

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