"How to Turn a Coke Can Into an Eavesdropping Device"

According to a team of academics from Ben-Gurion University of the Negev, a soda can, a smartphone stand, or any bright lightweight desk decoration could lead to eavesdropping. This can even be done in a soundproof room if an attacker can see the object. The team demonstrated that audio conversations could be captured from up to 35 meters or nearly 114 feet away at the volume of a typical meeting or conference call. This demonstration builds on previous research on optical speech eavesdropping. Using a telescope, the researchers gathered light reflected from an object near the speaker. They also used a photodiode (light sensor) to sample changes in the light when the object vibrated. Ben Nassi, an information security researcher at the university, says a lightweight device with a shiny surface reflects the signal with enough fidelity to retrieve the audio. This eavesdropping experiment is not the first time researchers tried to recover audio from nearby objects using side-channel techniques. For example, in 2016, researchers revealed how to convert a computer's audio-out jack to an audio-in jack and use speakers as microphones. A group of MIT researchers discovered a way to capture sound waves using a potato chip bag in 2014. According to Raz Swissa, a researcher at Ben-Gurion University of the Negev, the MIT research is similar to the technique that the Ben-Gurion University researchers pursued, except the exploitation required more restrictive placement of the reflective object and significant processing power to recover the audio. The earlier technique cannot be used in real-time since it demands a large amount of processing resources to restore only a few seconds of sound. A detectable light signal is also required for other well-known approaches, such as a laser microphone. Therefore, the researchers concentrated on developing a process that could be carried out through everyday objects already present in the target area and readily available instruments. This article continues to discuss the technique that allows attackers to recover voice audio from meetings if there are shiny lightweight objects nearby. 

Dark Reading reports "How to Turn a Coke Can Into an Eavesdropping Device"