Reviving TEMPEST Attacks With An Injected Signal

This was able to recover audio from wired headphones, wireless headphones, and a wireless landline, and detect the state of a smart lamp and a smart fan. All of this worked over short distances, even through walls, and with a power amplifier, the range increased to 30 meters. Even with multiple devices present, they could focus on one by tuning the injection frequency to resonate with its internal antennas. Perhaps most impressive (or concerning) was a demonstration with the VoIP phone: the researchers were able to listen in on the person speaking, clone that person’s voice, synthesize new speech in that voice, and remotely inject it onto the phone call, altering the call in real time.

Most of the attacks seemed too hard to perpetrate in the places where it'd be interesting. Getting a high power transmitter into a secure facility would be exceptionally difficult with a high risk of getting caught.

But the demo with the VoIP phone seems especially interesting for places like foreign embassies.