United States-TEMPEST
Reports have indicated the existence of another NSA project that is designed to capture computer signals (such as keystrokes or monitor images) through walls or from other buildings, even if the computers are not linked to a network. Details about this project, which is apparently codenamed TEMPEST, are only just becoming available. One NSA document, entitled "Compromising Emanations Laboratory Test Requirements, Electromagnetics", was prepared by the NSA's Telecommunications and Information Systems Security group. It describes test procedures for measuring the radiation emitted from a computer -- both through radio waves and through telephone, serial, network, or power cables attached to it. A second document the NSA released describes the agency's "Technical Security Program," which is responsible for assessing electronic security and providing "technical security facility countermeasures." Two subsequent research articles how the blinking patterns of LEDs and changes in the light intensity of cathode-ray tube displays, even from a distance, can allow someone to eavesdrop on the data passing through a given computer.
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