Amateur Radio Activities
(From the NSA Handbook)

Amateur radio (ham radio) activities are known to be exploited by hostile intelligence services to identify individuals with access to classified information; therefore, all licensed operators are expected to be familiar with NSA/CSS Regulation 100-1, "Operation of Amateur Radio Stations" (23 October 1986). The specific limitations on contacts with operators from communist and designated countries are of particular importance. If you are an amateur radio operator you should advise the Security Awareness Division (M56) of your amateur radio activities so that detailed guidance may be furnished to you.