It’s a pattern that no doubt repeats itself daily in hundreds of millions of offices around the world: People sit down, turn on their computers, set their mobile phones on their desks and begin to work. What if a hacker could use that phone to track what the person was typing on the keyboard just inches away?
A research team at Georgia Tech has discovered how to do exactly that, using a smartphone accelerometer-the internal device that detects when and how the phone is tilted-to sense keyboard vibrations and decipher complete sentences with up to 80 percent accuracy. The procedure is not easy, they say, but is definitely possible with the latest generations of smartphones.
“We first tried our experiments with an iPhone 3GS, and the results were difficult to read,” said Patrick Traynor, assistant professor in Georgia Tech’s School of Computer Science. “But then we tried an iPhone 4, which has an added gyroscope to clean up the accelerometer noise, and the results were much better. We believe that most smartphones made in the past two years are sophisticated enough to launch this attack.”
Previously, Traynor said, researchers have accomplished similar results using microphones, but a microphone is a much more sensitive instrument than an accelerometer. A typical smartphone’s microphone samples vibration roughly 44,000 times per second, while even newer phone’s accelerometers sample just 100 times per second-two full orders of magnitude less often.
Plus, manufacturers have installed security around a phone’s microphone; the phone’s operating system is programmed to ask users whether to give new applications access to most built-in sensors, including the microphone. Accelerometers typically are not protected in this way.
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