Keylogging through the power cable

The BBC's Technology site has published an interesting story regarding computer security. However, what makes this piece of news a little different is that it does not regard viruses, or trojans, yet instead an electrical footprint which remains on a circuit board every time a key is typed.

Security researchers have been investigating this phenomenon, and have discovered that poor shielding on some keyboard cables, can leak potentially lucrative information regarding each typed character. This information is not logged via some program upon the computer being snooped, instead the analysis is drawn to the information appearing onto power circuits, where it can be deciphered into readable material.

It should be said that this research only regards keyboards which use the (almost redundant) PS/2 connection. The pair of researchers from the security firm Inverse Path, explain this occurrence thus:

"The six wires inside a PS/2 cable are typically close to each other and poorly shielded. This means that information travelling along the data wire, when a key is pressed, leaks onto the earth (ground in the US) wire in the same cable. The earth wire, via the PC's power unit, ultimately connects to the plug in the power socket, and from there information leaks out onto the circuit supplying electricity to a room."

It is further explained that this data which travels along PS/2 cables does so one bit at a time, and uses a clock speed far lower than any other PC component. Both these qualities make it easy to pick out voltage changes caused by key presses and decipher them accordingly.

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

Although this research might seem a little redundant even in its youth; given the age of the connectors it is being tested upon, the researchers assure that it is still a work in progress. They also expect the testing equipment to become more sensitive as it is refined. This, i can only interpret as a piece of research which hopes to potentially cover some different connections in the future, perhaps USB or Firewire, and analyze the electrical footprints they leave upon a circuit.

Tests so far have been accurate and have been demonstrated over relatively short distances between 1 and 15 meters of the target machine.