Turn a Coke can into a listening device?

BLACK HAT ASIA — According to a team of researchers from Ben-Gurion University of the Negev, a soda can, a smartphone stand or a shiny, lightweight desk decoration could pose a threat to eavesdropping, even in a soundproofed room, if an attacker can see the object. †

At Thursday’s Black Hat Asia security conference, and with the goal of building on previous research into optical speech tapping, the research team showed that audio conversations can be captured at the volume of a typical meeting or conference call at up to 35. meters, or about 114 feet, away. The researchers used a telescope to collect the light reflected from an object near the speaker and a light sensor — a photodiode — to measure the changes in light as the object vibrated.

A lightweight object with a glossy surface will reflect the signal with enough fidelity to restore the audio, said Ben Nassi, an information security researcher at the university.

“Many shiny, lightweight objects can serve as optical implants that can be used to restore speech,” he said. “In some cases, they’re completely harmless objects, like a smartphone stand or an empty drink can, but all of these devices — because they share the same two characteristics, they’re lightweight and shiny — can be used to listen in if there’s enough light.” .”

The eavesdropping experiment isn’t the first time researchers have attempted side channel attacks that pick up audio from surrounding objects.

Improvement of previous optical eavesdropping
For example, in 2016, researchers demonstrated ways to transform the audio-out jack on a computer into an audio-in jack, using speakers as microphones. In 2014, a group of MIT researchers found a way to use a bag of chips to pick up sound waves. And in 2008, a group of researchers created a process to record the keys typed on a keyboard based on their sounds and the time between keystrokes.

The MIT study is similar to the technique pursued by the researchers at Ben-Gurion University, except that the exploitation required more restrictive placement of the reflective object and required significant processing power to restore the audio, Raz Swissa said. a researcher at Ben-Gurion University of the Negev.

“This one [older] The method cannot be applied in real time because it takes a lot of computing power to recover just a few seconds of sound,” he said. And other well-known techniques, such as a laser microphone, require a detectable light signal to work.

So the researchers focused on creating a process that can be achieved with everyday objects already in the targeted area and using tools that are readily available. Using objects 25 centimeters — about 10 inches — away from the speaker, the researchers were able to capture fluctuations in the light reflected off it up to 35 meters away. The restored speech was quite clear at 15 meters and somewhat intelligible at 35 meters.

In general, the experimental setup, which the researchers call the Little Seal Bug, could be used to capture audio with everyday objects. The attacker may be off-target, less detectable, while the low computing requirements allow real-time recording.

Big seal, little seal and beyond
The Little Seal Bug is a nod to a well-known early spy incident known as the Great Seal Bug. In 1945, the Soviet Union gifted the American ambassador a crimson embossed eagle that appeared to celebrate the collaboration between the US and the Soviet Union to defeat Nazi Germany. But the Great Seal also had a hidden audio recorder that allowed Soviet spies to eavesdrop on high-level conversations inside the embassy.

Likewise, the little seal could use common objects around an office to capture audio via reflected light. In addition, most mobile devices come with a photo sensor that does not require special permission to access. While the researchers haven’t come up with an attack chain using the sensor, such a resource could very well be used by future attackers.

However, there are many more likely threats from espionage attacks, Nassi said. From compromising systems with malware and capturing the audio that way, to using microphones already embedded in Internet of Things devices, such as AI assistants and video cameras, our world is quickly filling up with potential eavesdropping devices.

“A smartphone, a laptop, an IP camera and a smartwatch are probably more risky in terms of privacy than these devices or objects,” he said.

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