Tempest, van Eck phreaking, and High Tech Tinfoil

In 1985, Wim van Eck published a paper entitled "Electromagnetic Radiation from Video Display Units: An Eavesdropping Risk?" in which he explains how to "sniff" data off of others monitors. It was somewhat incomplete so that you had to do some real work to build a working sniffer (some would say that this was done at the behest of the government to basically prevent "script kiddies" of the 80's from building these things en masse). This paper started a public awkening of what the government had known for years... you can sniff almost any kind of electronic data from it's source without having to be in physical contact with it. Computer screens are great examples, but printer cables, network cables, SCSI cables all give off EM radiation, and all can be sniffed with enough know-how.