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Researchers find a way to snoop on you through your phone’s vibration motor

Cover up your webcam, disable microphone access and put on your tinfoil hat — but it won’t make any difference, because the Illuminati can get at you through your phone’s vibration motor now. Well, kind of, anyway. Your best defense? Talk in a high voice.

The “VibraPhone” research comes from Romit Roy Choudhury and Nirupam Roy, associate professor and PhD candidate, respectively, at the Electrical and Computer Engineering school of the University of Illinois at Ubana-Champaign.

It’s a surprisingly simple idea, really: A vibration motor is really like a tiny speaker. And every speaker can be a microphone. Think about it.

Okay, if it’s not obvious — a magnetic surface that has its position controlled by an applied voltage can also be arranged so that its own position changes that voltage instead. One way it’s a speaker, the other way it’s a microphone.


So it’s not “fundamentally surprising” that the vibration motor could be used to pick up sounds, the two wrote in their paper (PDF), which will be presented later this month at MobiSys in Singapore. But “the fidelity to which this is possible has been somewhat unexpected.”

First though, it should be made clear that this attack can’t be executed over the air or anything. The motor has to be physically rewired, although it’s a simple enough job and could be done in a minute or two. A less invasive technique is conceivable, though. “It may be possible to exploit the power controller chip to collect the voltage fluctuation in the vibration motor,” Roy wrote in an email to TechCrunch. “However, we did not investigate this possibility.”

At any rate, once the reconfiguration is done, the vibration motor begins turning the vibrations it encounters into voltage variations, which Roy and Choudhury showed can be reconstructed into waveforms.

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