New Eavesdropping Technique Can Capture Audio from Headphones Through Walls

Researchers in China have developed a new eavesdropping method called InjectEave that can capture audio signals from headphones, landline handsets and other devices from up to 30 metres away, including through walls. Unlike previous attacks that try to passively pick up faint electromagnetic emissions, InjectEave actively transmits a radio signal that interacts with non-linear hardware components inside a device, such as amplifiers and analog-to-digital converters. This interaction causes the device to unintentionally leak the audio signal it is processing, making it detectable to an attacker nearby.

The research team, based at The Hong Kong University of Science and Technology and The Hong Kong Polytechnic University, confirmed the vulnerability on multiple commercial products from brands including Sony, HP and Philips. The findings were presented as an academic paper at USENIX Security 2026, and the specific frequency details required to carry out the attack have been withheld from publication.

While this is a research demonstration rather than an active threat seen in the wild, it highlights a growing category of side-channel attacks that exploit hardware behaviour rather than software flaws. These attacks are harder to detect with traditional security tools because they do not involve malware or network intrusion, instead relying on physical proximity and specialised equipment.