InjectEave: an attack that intercepts analog audio signals

InjectEave is a novel side-channel attack targeting the analog audio signals emitted by headphones and headsets. Headphone components convert digital audio to analog signals and amplify them to drive speakers, producing weak electromagnetic emissions. These emissions are typically too faint to intercept directly. InjectEave overcomes this by using an external radio transmitter that beams a signal at a frequency (1 to 8 MHz) that modulates the headphone emissions, effectively amplifying the low-frequency audio signals (20 Hz to 20 kHz). The modulated signal can be intercepted from several meters away with sensitive antennas and analyzed to reconstruct intelligible audio. Experiments on three wireless headphone models, two wired headsets, and a wired telephone headset demonstrated the attack's feasibility, including two-way audio interception on the telephone headset. The attack's main limitations are the need for close proximity and device-specific frequency tuning. This research highlights the difficulty of protecting analog signals from side-channel electromagnetic eavesdropping, as encryption does not apply once data is converted to analog form.

The InjectEave attack enables attackers to eavesdrop on audio output from headphones and headsets by intercepting analog electromagnetic emissions. This compromises the confidentiality of voice calls and conversations even when digital encryption protects the data stream. The attack can capture intelligible audio from wireless and wired headphones within a range of one to six meters and can intercept two-way audio on wired telephone headsets. However, the attack requires physical proximity and specialized equipment, limiting its practical exploitation. It exposes a fundamental vulnerability in analog audio components that cannot be mitigated by encryption or standard digital security controls.

There is no known patch or fix for the InjectEave attack as it exploits inherent physical properties of analog components in headphones. The attack requires close proximity and device-specific tuning, which limits its feasibility. Users should be aware that encryption protects digital data but cannot secure analog signals once converted. Physical security measures to prevent close-range attacks and using headphones with minimal electromagnetic emissions may reduce risk, but no definitive mitigation exists. Monitor vendor advisories for any future hardware or firmware countermeasures.