Image from Shutterstock.com

As I was writing a story on the latest interview with Edward Snowden, I read a section where the fugitive NSA whistleblower’s friends warned author James Bamford (himself a former NSA employee and whistleblower) that a smart phone could still be used as an eavesdropping device even if the battery is removed.

That’s not possible, I thought.

Then I came across another story in Wired that Stanford University researchers and Israel’s defense research group Rafael plan to present a technique at a conference next week for using a smartphone’s gyroscope to eavesdrop on nearby conversations in a room. In case you don’t know the gyroscope are sensors that tell the phone whether its in horizontal or vertical position.

With the help of software, the researchers  found that the gyroscopes are sensitive enough to also pick up some sound waves, turning them into crude microphones.

For now, author Andy Greenberg writes, “the researchers’ gyroscope snooping trick is more clever than it is practical. It works just well enough to pick up a fraction of the words spoken near a phone. When the researchers tested their gyroscope snooping trick’s ability to pick up the numbers one through ten and the syllable “oh”—a simulation of what might be necessary to steal a credit card number, for instance—it could identify as many as 65 percent of digits spoken in the same room as the device by a single speaker. It could also identify the speaker’s gender with as much as 84 percent certainty. Or it could distinguish between five different speakers in a room with up to 65 per cent certainty.”

Briefly, it’s able to do it because the gyroscope is a tiny vibrating plate on a chip, which can pick up vibrations in nearby air. Custom speech recognition software  built by the researchers interprets the signals.

It’s a long way from being perfected — at least the researchers’ version is. The NSA’s version? Sorry, we can’t tell you.