Israeli researchers have discovered that it is possible to reconstruct conversations held in a room by remotely capturing the micro-vibrations of lighted bulbs.
If you are concerned that microphones may be hidden somewhere at home to spy on your conversations, you might as well be wary of… your lamps. Not that they are the ideal place to hide a cookie (that is in the movies): simply, they can themselves act as cookies. More precisely, their bulbs are lit. This is the result of the work of a team of Israeli researchers from the Ben-Gurion University of the Negev and the Weizmann Institute of Sciences. Published online, this research will be presented at the annual Black Hat cybersecurity conference in early August 2020.
A few years ago, the American Massachussetts Institute of Technology succeeded in reconstructing sounds (conversations, music) by filming the micro-vibrations they caused on plants or a packet of crisps . The approach of the Israelis is similar except that it is the micro-vibrations of the bulbs and the induced changes in the angles and the light emissions which are captured, of the order of a millidegre.
A spy technique called Lamphone
Called Lamphone, this remote listening technique involves the use of an electro-optical sensor. The optical signal then passes through an algorithm which analyzes it, does not take account of parasitic noises, isolates vibrations and translates them into sounds, all in real time. Following various tests, the researchers were even able to isolate several different acoustic signals compiled on the same audio file played by an enclosure.
The team conducted an experiment in real situations. Three telescopes with different lenses (10, 20 and 35 cm) were posted on a pedestrian bridge 25 meters away from the target: an office on the third floor of a building, light on but curtains down, and where no sound was obviously audible. The telescopes were in turn fitted with the same electro-optical Thorlabs sensor, the photodiode of which converts a light signal into an electrical signal.