Two teams of researchers from the United States and China discovered a method through which any hard drive can be used as a microphone. So, computers equipped with hard drives might be used for espionage even if the computer’s microphone is disabled. The way this is possible is complicated – but not impossible – and it comes with technical and physical limitations.
The discoveries made by researchers from the Michigan University and Zhejiang University will be published in a study named ” Hard Drive of Hearing: Disks that Eavesdrop with a Synthesized Microphone”.
This paper is signed by Andrew Kwong, Wnyuan Xu and Kevin Fu, who discovered a method through which the vibrations of the reading head of the hard drive can be transformed into audio files.
The method requires the firmware of the hard drive to be modified, something that might be “planted” into a target computer through older hacking methods such as infecting the target computer with a virus that does that, phishing or through direct access to the computer. Once modified, the hard drive firmware can be programmed to record surrounding noises, the recordings being good enough to identify a song through the Shazam app.
“Our research proves that some mechanical components of the magnetic hard drive behaves as microphones and they have enough precision to distinguish human voice. These microphones detect human voice with a pretty high precision to allow the recorded sound to be recognized by Shazam” researchers said.
There are, however, some limitations. For example, to properly understand human voice the discussion needs to happen at an intensity of 85 dB. From 75 dB up the voice is hard to understand. To recognize a song, it had to be rendered at 90 dB. Researcher say that there are different software and hardware methods that can “clean up” the audio signal and amplify human voice to be recognized easier. Also, when the recording is being done at a high volume, it can detect sounds at a frequency of up to 17.28 kHz, which is very close to 20 kHz limits of the human hearing, being even of better quality than the sound of a phone which has a limit of 8 kHz.
Regular users should not worry if they are still using hard drives in their computers because most hackers do not pick targets at random, but State agencies, big corporations and other important people might need to steer clear of such storage methods in the future in order to avoid espionage.