Researchers: Power Sockets can Detect Keyboard Input

Dennis Faas's picture

Researchers at security firm Inverse Path plan to demonstrate how standard power sockets (used in a home, for instance) can be used to eavesdrop on what is being typed onto a computer keyboard. They plan to make a presentation at the Black Hat Security conference taking place in Las Vegas from July 25-30 this year.

The researchers found that poor electrical shielding on some keyboard cables can result in data being leaked into power circuits. Analyzing such information allowed the researchers to see what was being typed on a keyboard.

So far, demonstrations of the attacks have worked at distances up to 15 meters, but with some refinement, the attacks could work over much longer distances.

Research Focused on PS/2 Connector Cables

Andrea Barisana and Daniele Bianco plan to show that information leaks in the most unexpected ways and can be retrieved. Their research was focused on the cables that are used to connect PS/2 keyboards to desktop PCs.

The attacks work because the six wires enclosed inside the PS/2 cable are typically close to each other and poorly shielded, meaning that the information traveling across the data wire leaks onto the earth/ground wire in the same cable when a key is pressed.

The researchers found that data travels along PS/2 cables one bit at a time and uses a clock speed that is far lower than any other PC component. Both qualities combined make it easier to pick out the voltage changes that are caused when the keys are pressed.

Blame the Ground Wire

The information leaks out onto the power circuit because the ground wire ultimately connects to the plug in the power socket.

Researchers used a digital oscilloscope to gather data about voltage changes on a power line. Filters were used to remove those changes by anything other than the keyboard. (Source:

The method was demonstrated working over distances of 1, 5, 10 and 15 meters from a target computer. Their research is a work-in-progress and the pair expects the equipment to get more sensitive as it is refined.

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