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.