Did you think your calls were private? This new spying technique can transcribe what you say.

A group of researchers at Pennsylvania State University (United States) has discovered a disturbing way to violate people's privacy while they are talking on the phone . Using millimeter-wave radar, along with an artificial intelligence-based voice recognition system, they were able to capture and transcribe telephone conversations from three meters away, with an accuracy of approximately 60%.

But how does this alarming technique work? A millimeter-wave radar detects vibrations from a telephone's earpiece speaker during a call, even when the sound is inaudible to humans and conventional microphones. A voice recognition model—based on the open-source Whisper technology—is then adapted to process the signals picked up by the radar, using a technique called "low-range adaptation."

The result is quite surprising, since even with errors in signal processing, the technique can transcribe calls with 60% accuracy in a vocabulary of 10,000 words. Furthermore, while the technique is far from perfect, researchers have found that such a system can have serious security implications, as it can reveal sensitive information .

On the other hand, according to the journal Interesting Engineering , this technique is based on a 2022 project, in which the research group achieved up to 83% accuracy when recognizing ten predefined words using a similar approach.

This technique is similar to lip reading.

The research group explains that this method is similar to lip reading , meaning that even if you only manage to grasp 30% to 40% of the words, with the proper context, it's possible to reconstruct a large part of the conversation . Furthermore, the system's results, while not 100% accurate, can reveal sensitive information if combined with previous data or manual review.

On the other hand, author Suryoday Basak reveals to Interesting Engineering the potential risks posed by this technology: "Similar to how lip readers can use limited information to interpret conversations, the output of our model allows us to infer parts of a telephone conversation from a few meters away ."

He adds that the goal of this technique is to explore whether these tools can be used by malicious actors to remotely eavesdrop on telephone conversations : "Our findings suggest that this is technically feasible in certain circumstances, and we hope this will raise public awareness so people are more aware during sensitive calls."

However, in the future, efforts are planned to develop protective measures to secure personal conversations from this type of remote surveillance.

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