Former Chief of the CIA Angola Task Force John Stockwell has a chapter in his 1978 book In Search of Enemies: A CIA Story called "CIA v. Congress" in which he describes at length the CIA "feeding" Congress "patently false information about the ongoing Angolan operation, depriving them of the full information which they needed to perform their constitutional role." The CIA's interest in controlling the access of Congress to information about the CIA's Angola operations was so great that Stockwell states that (see p. 228) the CIA kept a "soft file" on Senator Richard "Dick" Clark, a member of the Senate Foreign Relations Committee, who was tasked by the Committee to look into the Angola program in 1975.
What's a "soft file"? Stockwell explains:
The "soft file on Senator Clark" was useful when he traveled to the region for a Senate fact-finding trip. Stockwell notes that the file contained, among other things, "a cable from headquarters to Kinshasa instructing the chief of station to see Mobutu [Sese Seko] and Holden Roberto and prep them for their meeting with Senator Clark." Stockwell states that when he questioned at a CIA staff meeting whether it was appropriate for the CIA to tell African leaders "what they should and should not tell" the Senator on his visit, he was met with a "chorus of sharp voices" indicating that the CIA had "already told Clark everything he needed to know."Since the Freedom of Information Act, the agency increasingly uses a system of "soft," "unofficial," or "convenience" files for sensitive subjects, especially any involving surveillance of Americans. Such files are not registered in the agency's official records system, and hence can never be disclosed under the FOIA.
Stockwell further notes that although the rest of the CIA's "file on Senator Clark was 'soft,' and therefore safe from the Freedom of Information Act" the specific cable he described was duplicated in the central file of CIA cables and noted that it was "admitted that it wasn't very smart having a cable like that in the files" because the CIA could eventually "expect the Senate to close the program down and investigate it" and the Senate "just might get their hands on such a cable and kick up a fuss."
The CIA's own 2008 history of its relationship with Congress The Agency and the Hill written by L. Britt Snider, picks up the aftermath of Stockwell's revelations (Ch. 9, p. 282), which involved an investigation by the SSCI and a fallout that bears a striking resemblance to recent days . . .