Communications of the ACM
Researchers Sniff Pc Keyboard Strokes From Thin Air
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Research teams from the Ecole Polytechnique Federale de Lausanne in Switzerland and Inverse Path say they have discovered new techniques to read what a person is typing. The techniques developed by the two separate teams are based on the electromagnetic radiation that is generated whenever a computer keyboard is used.
The Ecole Polytechnique team used an oscilloscope and an inexpensive wireless antenna to pick up keystrokes from almost any keyboard. The researchers found four different ways of recovering keystrokes, with the keyboard's cabling and nearby power wires acting as antennas for the electromagnetic signals, enabling the researchers to read keystrokes with 95 percent accuracy over a distance of 20 meters. Even encrypted wireless keyboards are not safe from this attack. Laptop keyboards are harder to read, because the cable between the keyboard and the computer is shorter, but they can still be read.
Inverse Path researchers discovered a way to read keyboard strokes by plugging into a power socket, though this technique only applies to older PS/2 keyboards, which have ground wires that connect directly to the electrical grid. The ground wire passes through the PC and into the electrical grid, where another computer, an oscilloscope, and about $500 worth of equipment can be used to read what is being typed. The researchers can pick up a keyboard's signals even on a crowded power grid because PS/2 keyboard emanate radiation at a standard, very specific frequency.
From IDG News Service
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