Security News > 2020 > June > Spies Can Listen to Your Conversations by Watching a Light Bulb in the Room

You might not believe it, but it's possible to spy on secret conversations happening in a room from a nearby remote location just by observing a light bulb hanging in there-visible from a window-and measuring the amount of light it emits.

A team of cybersecurity researchers has developed and demonstrated a novel side-channel attacking technique that can be applied by eavesdroppers to recover full sound from a victim's room that contains an overhead hanging bulb.

To achieve this, the setup consists of a telescope to provide a close-up view of the room containing the bulb from a distance, an electro-optical sensor that's mounted on the telescope to convert light into an electrical current, an analog-to-digital converter to transform the sensor output to a digital signal, and a laptop to process incoming optical signals and output the recovered sound data.

"We analyze a hanging bulb's response to sound via an electro-optical sensor and learn how to isolate the audio signal from the optical signal. Based on our analysis, we develop an algorithm to recover sound from the optical measurements obtained from the vibrations of a light bulb and captured by the electro-optical sensor."

Given the effectiveness of the attack relies heavily on the light output, the countermeasures proposed by the paper's authors involve reducing the amount of light captured by the electro-optical sensor by using a weaker bulb and a curtain wall to limit the light emitted from a room.

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