Security Classification

Security Classification

All documents that contain classified information have to be marked with codes that detail appropriate control procedures. These are usually presented at the top of the document, and occaisonally at the beginning of each sub-heading and paragraph. They are usually comprised of three elements, separated by double slashes:


Further information on security classification and distribution codes can be found at

There are three main classification levels:


After the security classification, there is a series of Sensitive Compartmented Information (SCI) codes that further control access to the document. These are usually codewords, the meaning of which is unknown in some cases. There may be around 100-300 SCI compartments, grouped into about two dozen different control systems. Some of the codes that are known include:

  • COMINT / Special Intelligence (SI)

    This control system is for communications intercepts or Signals Intelligence, and contains various sub-control systems and compartments, identified by an abbreviation or codeword. They usually follow the code COMINT or SI with a hyphen. They include:

    • VTK : Very Restricted Knowledge
    • ECI : Exceptionally Controlled Information
    • G : Gamma
    • D : Delta

    This is a "controlled access signals intelligence program" created under presidential authorization after the attacks of September 11th. It includes information related to the President's Surveillance Program (PSP), the Terrorist Surveillance Program (TSP) and bulk telephony and metadata collection by the NSA.


This control system is reserved for finalized intelligence products. ENDSEAL information is always classified as Special Intelligence (SI). Documents with this classification are intended for dissemination to various consumers within the Intelligence Community.


    This control system is reserved for the products of overhead collection systems, including satellites and reconnaissance aircraft.


    This control system is used for compartments protecting new sources and methdos during research, development and acquisiton done by the National Reconnaissance Office (NRO).


    This control system has been developed for Geospatial Intelligence (GEOINT) produced by the National Reconnaissance Officer (NRO).

  • HUMINT Control System (HCS)

    This control system is for protecting Human Intelligence (HUMINT), which is derived from information collected or provided by human sources.

  • STRAP 1 / STRAP 2 / STRAP 3

    These are code terms for GCHQ documents, STRAP 1 being the lowest level, and STRAP 3 being the highest. No STRAP 3 documents have been published as of yet.

Security Classification