An Optical Spy Trick Can Turn Any Shiny Object Into a Bug
upstart writes:
An Optical Spy Trick Can Turn Any Shiny Object Into A Bug:
At the Black Hat Asia hacker conference in Singapore this May, researchers from Israel's Ben Gurion University of the Negev plan to present a new surveillance technique designed to allow anyone with off-the-shelf equipment to eavesdrop on conversations if they can merely find a line of sight through a window to any of a wide variety of reflective objects in a given room. By pointing an optical sensor attached to a telescope at one of those shiny objects-the researchers tested their technique with everything from an aluminum trash can to a metallic Rubik's cube-they could detect visible vibrations on an object's surface that allowed them to derive sounds and thus listen to speech inside the room. Unlike older experiments that similarly watched for minute vibrations to remotely listen in on a target, this new technique let researchers pick up lower-volume conversations, works with a far greater range of objects, and enables real-time snooping rather than after-the-fact reconstruction of a room's audio.
[...] The researchers' trick takes advantage of the fact that sound waves from speech create changes in air pressure that can imperceptibly vibrate objects in a room. In their experimental setup, they attached a photodiode, a sensor that converts light into voltage, to a telescope; the longer-range its lenses and the more light they allow to hit the sensor, the better. That photodiode was then connected to an analog-to-digital converter and a standard PC, which translated the sensor's voltage output to data that represents the real-time fluctuations of the light reflecting from whatever object the telescope points at. The researchers could then correlate those tiny light changes to the object's vibration in a room where someone is speaking, allowing them to reconstruct the nearby person's speech.
The researchers showed that in some cases, using a high-end analog-to-digital converter, they could recover audible speech with their technique when a speaker is about 10 inches from a shiny metallic Rubik's cube and speaking at 75 decibels, the volume of a loud conversation. With a powerful enough telescope, their method worked from a range of as much as 115 feet. Aside from the Rubik's cube, they tested the trick with half a dozen objects: a silvery bird figurine, a small polished metal trash can, a less-shiny aluminum ice-coffee can, an aluminum smartphone standard, and even thin metal venetian blinds.
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