What is TEMPEST?
TEMPEST is the study of electromagnetic emissions from data processing equipment such as computers, networking gear and printers. Such emissions can be collected and processed to reveal information that is being stored, processed or displayed. This presents the security risk of sensitive and/or classified information being unintentionally compromised to adversaries. TEMPEST products are created to reduce or eliminate the electromagnetic emissions. Most information concerning TEMPEST techniques and specifications is classified by the United States Government and is not available for general use.
The National Security Agency manages the TEMPEST Certification Programs (TCP) that consist of three closely related NSA programs: the Certified TEMPEST Products Program, the Certified TEMPEST Test Services Program and the Zoned Equipment Program. These programs involve partnerships with industry. Further information can be found at their site: http://www.nsa.gov/applications/ia/tempest/index.cfm.
The USA and NATO use different names for similar TEMPEST levels. The following table is provided as a useful cross-reference.