Spies Can Listen To Chats From 100 Ft Away By Just Watching A Light Bulb

Spies have constantly found new ways of eavesdropping on conversations. With time, most of these techniques have been based on new technologies.

Yet another new one, however, just needs a hanging light bulb in a room.

reuters

A new technique by researchers from Ben-Gurion University of the Negev and the Weizmann Institute of Science lets one eavesdrop into a room from a long distance. Called "lamphone," the technique requires only a laptop, a telescope and a $400 electro-optical sensor.

The technique is based on the tiny vibrations that the sound in a room creates on the glass surface of a light bulb hanging in it. These vibrations in turn cause miniscule changes in light emanating from the bulb.

Anyone using the technique with the right equipment will be able to measure these changes in light output. A spy trained in this regard can hence can pick up sound from these changes, clear enough to find out the contents of any conversation or even recognize a piece of music, a new report by Wired claims.

The light bulb experiment

(Representative Image: Reuters)

The technique was recently proved to work by security researchers at Ben-Gurion namely Ben Nassi, Yaron Pirutin and Boris Zadov. In their experiments, the team placed a series of telescopes around 80 feet away from a target office's light bulb. At the eyepiece of each telescope, they put a Thorlabs PDA100A2 electro-optical sensor.

The team then used an analog-to-digital converter which converted the incoming electrical signals from those sensors to digital information.

Back in the room that was focused on by the telescopes, the team played music and speech recordings.

It was then that the team found out that the minute vibrations amounting to a few hundred microns were picked up by the sensors on the telescopes. Once the picked up signal was processed to filter out noise, the team was able to reconstruct the recordings of the sounds played inside the room.

Spying with light bulbs

The reconstructed sounds included a snippet of a speech from US President Donald Trump and a recording of the Beatles' "Let It Be." The signal readings through the sensors were clear enough for Google's Cloud Speech API and mobile app Shazam to translate and recognise the recordings respectively.

What makes the technique even more critical in its field of operation is that it enables spying in real time. In addition, it does not require cyber expertise to hack a device. "Any sound in the room can be recovered from the room with no requirement to hack anything and no device in the room," says Ben Nassi.

It can, however, be foiled just as easily, by simply closing the curtains of a room. So the next time you attempt a top-secret conversation in your room, make sure you check the windows curtains.