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Power Sockets Reveal Computer Keystrokes: Report

Posted on: Monday, 13 July 2009, 13:55 CDT

Computer keystrokes can be identified at power sockets, according to a new report by researchers at security firm Inverse Path. 

The research showed that poor shielding on some keyboard cables resulted in the leaking of information about each character a user typed.  Indeed, the researchers said they were able to determine which character a user was typing by simply analyzing the information leaking out onto the power circuits.

The keystrokes could be monitored at distances of up to 50 feet, but could occur at even longer distances, said researchers Andrea Barisani and Daniele Bianco.

"Our goal is to show that information leaks in the most unexpected ways and can be retrieved," said Barisani and Bianco in a paper describing their research, which focused on the cables used to connect PS/2 keyboards to desktop PCs.

The six wires inside a PS/2 cable are usually "close to each other and poorly shielded,” they said, meaning that information passing down the data wire whenever a key is pressed leaks onto the ground wire within the same cable.

The ground wire, by way of the PC's power unit, connects to the power socket, where information leaks out onto the circuit supplying power to a room.

Data travels along PS/2 cables one bit at a time using clock speeds far lower than any other PC component, making it easy to identify voltage changes triggered by keystrokes.

The researchers used a digital oscilloscope to collect data about voltage changes on a power line, then used filters to remove changes caused by anything other than the keyboard.

"The PS/2 signal square wave is preserved with good quality... and can be decoded back to the original keystroke information," the researchers wrote in the paper.

The experiment worked at distances of up to 50 feet from a target, suggesting it could work in an office or a hotel.

"The test performed in the laboratory represent a worst case scenario for this type of measurement, which along with acceptable results emphasizes the feasibility of the attack on normal conditions," the pair said, adding that their research was a "work in progress".

The equipment will likely get more sensitive as it is refined, they said.

The work will be demonstrated at the upcoming Black Hat conference in Las Vegas on July 25-30.

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On the Net:

• Inverse Path

Source: redOrbit Staff & Wire Reports

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