Researchers find way to listen in on headphones from afar

Chinese researchers have developed a technique called InjectEave that allows attackers to eavesdrop on signals handled by analog components in devices like headphones, landline handsets, and smart devices. This method, which is an EM side-channel attack, overcomes the challenge of faint RF signals by actively manipulating the signal.

By transmitting a signal in the 0-9 MHz range, an attacker can potentially modulate an otherwise difficult-to-detect audio signal, making it detectable by nearby equipment. InjectEave was tested on multiple commercial devices from brands such as Sony, HP, Philips, among others, revealing that these vulnerabilities could be exploited from up to 30 meters away, even through walls.

The attack targets non-linear components like amplifiers, analog-to-digital converters, power converters, and switching MOSFETs. Although hardware-based mitigations like twisted-pair wiring, shielding, and filtering can reduce the risk, they don't guarantee immunity since the leakage occurs through the analog path, making InjectEave impervious to digital defenses like encryption, masking, and randomization.