The ghostly woman’s voice pipes through the speakers, covered in radio static but her message intact from beyond — “The birch canoe slid on the smooth planks.”
A secret message from the other side? A spectral insight?
No, something much spookier: Voice recordings captured, secretly, from the radio frequencies emitted by ubiquitous, cheap microphones in laptops and smart speakers. These unintentional signals pass, ghost-like, through walls, only to be captured by simple radio components and translated back to static-filled — but easily intelligible — speech.
For the first time, researchers at the University of Florida and the University of Electro-Communications in Japan have revealed a security and privacy risk inherent in the design of these microphones, which emit radio signals as a kind of interference when processing audio data.
The attack could open up people to industry espionage or even government spying, all without any tampering of their devices. But the security researchers have also identified multiple ways to address the design flaw and shared their work with manufacturers for potential fixes going forward.
“With an FM radio receiver and a copper antenna, you can eavesdrop on these microphones. That’s how easy this can be,” said Sara Rampazzi, Ph.D., a professor of computer and information science and engineering at UF and co-author of the new study. “It costs maybe a hundred dollars, or even less.”