The text for this is probably up on the Internet somewhere, so someone who cares can impeach my memory. But what I remember being told is:
* Reporters assess anonymous sources carefully for why they are saying what they are saying (institutional interests, etc.)
* We should actually trust anonymous sources more than named sources (!). Whenever we hear a reporter citing an anonymous source from an intelligence service, that means that the reporter has done the utmost checking on whether the person is credible, has knowledge, and has a good reason to tell us
* Pretty much all reporting from intelligence services is from anonymous sources, because one of their rules is that they are not supposed to talk to reporters
* In fact, they take periodic polygraph tests where they are asked whether they have talked to reporters. The interviewer mused that anonymous sources must have to lie and hope that they pass the polygraph.
This is ridiculous, and no one who thinks about it for two minutes could not find it ridiculous. If everyone is given periodic polygraph tests where they are asked whether they have talked to reporters, then polygraph tests must not work. I find that pretty believable that they don't work well at all, but security services keep using them. Is it really credible that all of these "leaks" that favor the CIA's favored story really are from truth-tellers half-assedly hoping that they pass their next polygraph?
There's a much more credible story. All of these "leaks" -- the only things that reporters get -- are officially authorized leaks meant to tell a story that the CIA wants to be told. The people doing the leaking don't have to fear their next polygraph, because they were told to leak the information to the reporter. The reporters have every motive to play along, because if they don't, they don't get any news from this beat at all.
It's self-serving twaddle all around: from the CIA, from the reporters, from the listeners who want to believe the latest story that flatters their prejudices.