Research ‘net: The TEMPEST edition
When I was in the US Air Force, as part of the 438th Communications Group, we had a Group Readiness Center that contained a large board with the airfield equipment status, a safe with various drawers with different classification levels, a couple of encrypted communication systems, and… a couple of strange looking Z200 computers. The screen on these computers were covered with a fine mesh, and the power cables ran through a special cleaning box. What was the point of all this fanciness?
TEMPEST. The ability to gather information about what’s on a computer’s screen by examining the signals transmitted (unintentionally) from the monitor screen, power cable, and other electronics. This might seem odd, but essentially any wire is an antenna that can (and will) carry information from a computer; at some range, these signals can be detected and deciphered in a way that allows you to determine what the computer is processing. Screens are more fruitful, as the older style Cathode Ray Tube (CRT) displays essentially shoot a stream of electrons onto a piece of glass, some of which must leak, and hence can be picked up and decoded to see what’s on the screen from quite a distance Continue reading