Clicking, Clacking and Snooping: software can analyze the sounds of someone typing

The idea of snooping on keyboards has been around since the Cold War, when Soviet spies bugged typewriters in the American embassy in Moscow. Now researchers at the University of California, Berkeley, have found a way to turn the clicks and clacks of typing on a computer keyboard into a startlingly accurate transcript of what is being typed.

The researchers, including Doug Tygar, a professor of computer science, have developed software that can analyze the sounds of someone typing on a keyboard for 10 minutes and then piece together as much as 96 percent of what was typed.

The technique works because the sound of someone striking an “A” key, for example, is different from the sound of striking the “T,” according to Tygar. “Think of a Conga drum. If you hit a Conga drum on different parts of the skin, it makes a different tone,” he says. “There’s a plate underneath the keyboard [that is] being struck in different locations.”

One lesson from the study is that even randomly generated passwords are not secure. Tygar’s researchers were able to guess 90 percent of the five-character passwords they generated within 20 tries.

There is one easy step that users can take to conceal what they’re typing: Turn up the music. In noisy environments, it is more difficult to separate the keyboard sounds from other sounds, says Li Zhuang, one of the students who coauthored the paper.