Israeli scientists can eavesdrop conversations using a light bulb

By pointing a telescope at a hanging light bulb in the target room and passing the information through a standard laptop, researchers were able to eavesdrop from 25 meters away.

Tungsten light bulbs (illustrative) (photo credit: THOMAS WHITE / REUTERS)
Tungsten light bulbs (illustrative)
(photo credit: THOMAS WHITE / REUTERS)
Move over Q, Israeli scientists have revealed the latest technique for aspiring James Bonds wanting to eavesdrop on conversations, and it involves nothing more than pointing a telescope at an everyday light bulb.
Researchers from Ben-Gurion University of the Negev and the Weizmann Institute of Science found that minuscule vibrations in the light given off by a light bulb, caused by sound waves hitting its surface, are enough to harness conversations taking place inside a room in real time from up to 25 meters away - and all using standard equipment that costs under $1,000 in total. The invention has been dubbed the "lamphone."
"Any sound in the room can be recovered from the room with no requirement to hack anything and no device in the room," security researcher Ben Nassi told Wired. "You just need line of sight to a hanging bulb, and this is it."
Along with fellow researchers, Nassi conducted an experiment to test the technique, placing three telescopes of differing sizes on a pedestrian bridge within the line of sight of a hanging 12 watt LED light bulb in third floor office. They then mounted an electro-optical sensor used to convert light to electrical voltage to one telescope at a time, according to a paper the researchers plan to present at the Black Hat security conference in the USA in August.
The electrical voltage obtained was then passed through a computing script on the researcher's laptop and an equalizer to recreate the sound as it was played in the office.
Using this technique they were able to capture two songs played via speakers in the office - The Beatles' Let it Be and Coldplay's Clocks - using data from a single telescope. When played to Shazam, the song recognizing app, the songs were recognized. They also captured a line from a speech by Donald Trump, recreating the sound at a high enough quality for Google's Speech to Text API to transcribe it. The audios could not be heard by the human ear from the bridge, and the researchers say the range could easily be increased by upgrading the equipment used.
The set up is the most recent invention in a category of spyware techniques known as "side channel attacks," which aim to eavesdrop by measuring the interaction of sound waves with everyday objects such as a bag of potato chips or a window.
Nassi and his colleagues admit that the techniques "pose a great threat to privacy," however they point out that the technologies are currently limited in their application.
Similar devices include the Visual Microphone, which analyses video recorded via a telescope of an object in the target room to detect vibrations and recreate speech. However, although the technique is more versatile than the lamphone as it doesn't require a bulb to be within line of sight, it cannot be used in real-time as it requires video analysis to reconstruct the sound. By contrast, as the vibrating object utilized by the lamphone is a source of light, the sensor can pick up usable information at a lower resolution making it potentially significantly more practical.
"When you actually use it in real time you can respond in real time rather than losing the opportunity," Nassi told Wired.
Another device previously developed is the Laser Microphone, which uses a laser beamed into the victim's room and analyses the laser beams as it reflects off surfaces. But the laser can be detected by optical sensor; lamphone, on the other hand, is totally passive.
A third side channel attack method developed in 2014 utilized the gyroscope inside a compromised smartphone to pick up sounds, even if a hacking tool can't access the microphone, but again lamphone has an advantage as it is completely external and doesn't require a device to be compromised.
"It's a beautiful application of side channels," Stanford computer scientist and cryptographer Dan Boneh told Wired. "Even if this requires a hanging bulb and high decibels, it’s still super interesting. And it’s still just the first time this has been shown to be possible. Attacks only get better, and future research will only improve this over time."
Nassi said that the research paper is not intended to enable spying or law enforcers, but to illustrate what is possible.
"We want to raise the awareness of this kind of attack vector," he says. "We’re not in the game of providing tools."
But if you are concerned about the potential for being spied upon by someone using the lamphone, there is a low-cost countermeasure: you can simply draw your curtains, cutting off the line of sight.