Open Source Literature A3.7.1. It includes a wide range of activities from direct reconnaissance and observation to the use of informants and spies. Some intelligence requirements can best be satisfied by human source exploitation. Overt activities are performed openly without concealment. While some aspects may be classified, the overall activity is generally easily detected, or the sources are exploited in an open but discrete manner.
Sensitive activities fall between overt and clandestine.
Because their disclosure would be detrimental to the best interests of the United States, they require special protection from dis-closure, as well as concealment of the sponsor's identity. Clandestine activities must be conducted so that both the existence of the operation itself and the identity of the sponsor are secret. Mission route planning requires current intelligence on enemy defensive positions and capabilities. Targets can be detected and located through airborne direction finding techniques. Intelligence concerning enemy operational plans may be obtained through signal analysis or cryptologic procedures.