How can your phone conversations be eavesdropped?

(Dan Tri) - Millimeter wave radar can be used to eavesdrop on private phone calls.

A recent study by Pennsylvania State University (USA) has revealed an alarming eavesdropping method, capable of turning smartphones into surveillance tools through millimeter-wave radar technology.

Phone calls can be eavesdropped on using radar technology (Illustration: ST).

Research shows that when users activate the speakerphone, the surface of the phone (especially the speaker membrane) vibrates according to the sound emitted. Millimeter wave radar technology is capable of detecting these microscopic vibrations from a certain distance.

In the experiment, the scientists placed a radar device about 3 meters away from the phone. The vibration data collected from the phone's surface was then fed into a fine-tuned AI speech recognition model (the Whisper model). With just a 1% change in parameters, the AI model "learned" to decode the vibrations into speech.

The results were surprising: the model could transcribe speech with up to 60% accuracy across a 10,000-word vocabulary. While not perfect, the accuracy was comparable to lip reading—enough to grasp context and understand the gist of a conversation. Picking up keywords, proper names, or other important details was enough to pose a serious privacy risk.

The study is a warning about the potential misuse of seemingly innocuous technologies like radar for surveillance purposes. Millimeter-wave radar systems are increasingly common, embedded in everything from smartphones to sensors in self-driving cars. The possibility of them being used for eavesdropping poses a new threat that needs to be recognized.

The team's goal is not to create an eavesdropping tool, but to highlight potential vulnerabilities before they are exploited by bad actors. They hope the research will spur the development of countermeasures such as:

-Passive sound reduction: Use special materials or designs to reduce vibrations on the surface of the device.

-Active shielding: Generates random vibrations or noise to scramble the signal received by the radar.

As wireless technology and AI continue to advance, this research is an important reminder of the importance of protecting privacy in an increasingly connected world .

Source: https://dantri.com.vn/khoa-hoc/he-lo-cach-dien-thoai-tiet-lo-cuoc-tro-chuyen-cua-ban-20250813215625230.htm