I remember a related story from a TEMPEST advisory I read a few years ago.
The American embassy in Russia was being bombarded by very strong Radio Signals and it took them quite some time to figure out why they were doing that "old" trick again.
What they finally discovered was that while the security rated cords from the keyboards to the computers didn't normally radiate a signal that cord would resonate at a specific radio frequencies when there was a very strong radio signal applied.
What made this resonant signal from the cord bad was that it was also slightly modulated by the binary signals sent from the keyboard to the computer as the person typed.
In other words if you wanted to read most of the keystrokes of what someone was typing all you had to do was set up a couple of large parabolic or yagi type antennas that are well isolated from each other and in one of each others nulls or blindspots.
Then focus both on the known location of the computer your wanting to spy on and while one antenna beamed a radio signal the other antenna would pick up the modulated resonant signal from the computer's keyboard cord.
Because most keyboard cords are standardized you don't even have to know where the computers are in the embassy just bombard the entire embassy with the radio signal and use several other isolated antennas to scan for the resonant returns until you have the building mapped.
howard melton
God bless
The American embassy in Russia was being bombarded by very strong Radio Signals and it took them quite some time to figure out why they were doing that "old" trick again.
What they finally discovered was that while the security rated cords from the keyboards to the computers didn't normally radiate a signal that cord would resonate at a specific radio frequencies when there was a very strong radio signal applied.
What made this resonant signal from the cord bad was that it was also slightly modulated by the binary signals sent from the keyboard to the computer as the person typed.
In other words if you wanted to read most of the keystrokes of what someone was typing all you had to do was set up a couple of large parabolic or yagi type antennas that are well isolated from each other and in one of each others nulls or blindspots.
Then focus both on the known location of the computer your wanting to spy on and while one antenna beamed a radio signal the other antenna would pick up the modulated resonant signal from the computer's keyboard cord.
Because most keyboard cords are standardized you don't even have to know where the computers are in the embassy just bombard the entire embassy with the radio signal and use several other isolated antennas to scan for the resonant returns until you have the building mapped.
howard melton
God bless