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Wired Keyboards Keystrokes Can Be Hijacked From Up To 65 Feet Away

Swiss researchers from the Security and Cryptography Laboratory at Ecole Polytechnique Federale de Lausanne have found a variety of ways to eavesdrop on the sensitive messages computer users type by monitoring their wired keyboards. At least 11 models using a wide range of connection types are vulnerable.

The researchers are able to capture keystrokes by monitoring the electromagnetic radiation of PS/2, universal serial bus, or laptop keyboards. They’ve outline four separate attack methods, some that work at a distance of as much as 65 feet from the target. In one video demonstration, researchers Martin Vuagnoux and Sylvain Pasini sniff out the the keystrokes typed into a standard keyboard using a large antenna that’s about 20 to 30 feet away in an adjacent room.

A research paper on the discovery will be published after a peer-review process. Team members Martin Vuagnoux and Sylvain Pasini explain the findings:

To determine if wired keyboards generate compromising emanations, we measured the electromagnetic radiations emitted when keys are pressed. To analyze compromising radiations, we generally use a receiver tuned on a specific frequency. However, this method may not be optimal: the signal does not contain the maximal entropy since a significant amount of information is lost.

Our approach was to acquire the signal directly from the antenna and to work on the whole captured electromagnetic spectrum.

We found 4 different ways to fully or partially recover keystrokes from wired keyboards at a distance up to 20 meters, even through walls. We tested 11 different wired keyboard models bought between 2001 and 2008 (PS/2, USB and laptop). They are all vulnerable to at least one of our 4 attacks.

We conclude that wired computer keyboards sold in the stores generate compromising emanations (mainly because of the cost pressures in the design). Hence they are not safe to transmit sensitive information. No doubt that our attacks can be significantly improved, since we used relatively inexpensive equipments.

Although electromagnetic eavesdropping dates back to the mid 1980s, many of today’s keyboards have been adapted to prevent those attacks from working. The research shows that even these keyboards are vulnerable to electromagnetic sniffing.

Even still, it’s easy to see the limitations of such attacks. Interference from other televisions, lights, or other devices seems likely, although the video demonstrations suggest that the attacks work even when there are nearby computer monitors. The other thing that makes the attack unfeasible is the amount of sophisticated equipment required. Given all the fuss and expense, in most cases it would be easier to just sneak a keylogger onto the target’s machine.

The demonstration has already gotten the attention of other security researchers. The findings will be fleshed out in an upcoming research paper. The team released two online videos (here and here) demonstrating the research findings.

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