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DannyB writes:

From that unimpeachable source . . . The Reg . . .

From hard drive to over-heard drive: Boffins convert spinning rust into eavesdropping mic

It's not just the walls that have ears. It's also the hard drives.

Eggheads at the University of Michigan in the US, and Zhejiang University in China, have found that hard disk drives (HDDs) can be turned into listening devices, using malicious firmware and signal processing calculations.

For a study titled "Hard Drive of Hearing: Disks that Eavesdrop with a Synthesized Microphone," computer scientists Andrew Kwong, Wenyuan Xu, and Kevin Fu describe an acoustic side-channel that can be accessed by measuring how sound waves make hard disk parts vibrate.

"Our research demonstrates that the mechanical components in magnetic hard disk drives behave as microphones with sufficient precision to extract and parse human speech," their paper, obtained by The Register ahead of its formal publication, stated. "These unintentional microphones sense speech with high enough fidelity for the Shazam service to recognize a song recorded through the hard drive."

One limiting aspect of the described technique is that it requires a fairly loud conversation in the vicinity of the eavesdropping hard drive. To record comprehensible speech, the conversation had to reach 85 dBA, with 75 dBA being the low threshold for capturing muffled sound. To get Shazam to identify recordings captured through a hard drive, the source file had to be played at 90 dBA. Which is pretty loud. Like lawn mower or food blender loud.

The researchers acknowledge this is louder than most practical scenarios but they say they "expect that an attacker using state of the art filtering and voice recognition algorithms can substantially amplify the channel’s strength."

Hopefully SSD drives are not vulnerable.

Original Submission