A SIGINT Activity Designator (or SIGAD) identifies a signals intelligence (SIGINT) line of collection activity associated with a signals collection station, such as a base or a ship. For example, the SIGAD for Menwith Hill in the UK is USD1000.[1] SIGADs are used by the signals intelligence agencies of the United States, the United Kingdom, Canada, Australia and New Zealand (the Five Eyes).[2]
There are several thousand SIGADs including the substation SIGADs denoted with a trailing alpha character. Several dozen of these are significant.[3] The leaked Boundless Informant reporting screenshot showed that it summarized 504 active SIGADs during a 30-day period in March 2013.[4]