The GUNMAN Project
A most spectacular case of electronic espionage occurred in the 1980s, at the height of the Cold War, when it was discovered that Soviet intelligence had successfully implanted very sophisticated bugs in a large number of electronic typewriters at the U.S. embassy in Moscow.
It all started in August 1983, when a friendly government informed U.S. intelligence that they found a curious bug, implanted in equipment at their embassy. In response, the U.S. National Security Agency (NSA) sent communications security experts to their ally, to examine the bug. Its technology proved to be very sophisticated. The efforts, required to develop such technology, were of such a scale that NSA was convinced that this was not a single case.
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NSA technicians started the complex task of reverse-engineering the bugs. They turned out much more sophisticated than the specialists could ever have imagine. Metal cams were replaced by a non-ferromagnetic version that contained strong little magnets. These magnets caused magnetic disturbances when keys were depressed on the keyboard. The magnetic changes were picked up by the electronics, analysed and converted into a digital signal. The electronics were hidden completely invisible and sealed into a hollow support bar.
The signal was compressed into four-bit frequency selecting words. Up to eight four-bit characters could be stored in a circuit with tiny one-bit core memories. Only when the memory was filled completely (at irregular intervals due to the typists tempo) the data was sent in a very short burst transmission to a nearby listening post. The burst frequency range was selected deliberately in the same frequency band as Soviet television stations to hide the burst noise. The implants could be turned off remotely to avoid detection when security technicians would sweep the embassy for bugs.
