Electronic Weapons: Tappity Tap, Tap, Tap


September 19, 2005: September 19, 2005: Researchers have found yet another way to eavesdrop on a computer user. This technique is based on the sound that is made when a user strikes a key on a computer keyboard. Collect enough of these key noises, and based on what language the typist was using (all languages have a certain frequency of letter use), you can quickly "decode" those key noises and figure out what is being typed. This sort of predictive analysis is nothing new in cyberwar.  This works for email or IMs (Instant Messaging). You can also positively identify different email users by analyzing their text. That same technique is used to crack secret codes.  

For several decades, it has been possible, using fairly simple equipment, to pick up the small electronic signals your keyboard makes every time a key is hit, and analyze those to figure out what is being typed. All of these techniques, however, assume you can get pretty close to the keyboard in question. Electronic signals from keyboards are kept from going far by modifying keyboards. These are the U.S. "Tempest" grade keyboards often required when you are doing classified work. Getting a recording device near a keyboard may also prove difficult. So while the spies keep coming with great new tools, you still have to be at the right place at the right time to make it all work.

The technique of analyzing how an operator hit the keys is an old technique, going back over 150 years, when it was discovered that an experienced operator could tell who was on the other end of a telegraph line by the rhythm of how the telegraph key was hit. When computers came along, it was possible to automate that particular intelligence gathering task. Telegraph, via Morse Code, is still used in some intelligence work, because you can get the message through with modest equipment resources.


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