A long time prosecutor endorses my explanation of what went down with the Flynn/Kislyak overhear (the linked article cites my explanation extensively):
Based on my experience, this is the best explanation for where the Flynn/Kislyak call info came from. Regular interception of Russian Embassy Comms -- by Ambassador and others -- done by FBI Counter-Intelligence section on a continual basis.
Gen. Flynn was the subject of a CI investigation under Crossfire Hurricane/Razor. He would not have been "masked" in these "tech cuts" which are for internal use only. This kind of data is accumulated by intel analysts and then pushed out to case agents who have "need to know".
That would have included the CH/CR case agents. But they made no use of it in their investigation, which leads to the conclusion that they saw nothing in the "tech cuts" of the Flynn/Kislyak calls that supported the basis for opening the counterintel investigation on Gen. Flynn.
And this explains why on Jan 5 Comey had nothing of substance to tell Obama and others in terms of what Flynn and Kislyak had discussed -- only that the number of conversations seemed "unusual."
If there was anything truly sig[nificant] in any of the calls, the tech cuts would have been referenced in some investigation somewhere, and Comey would have gone over such information with Obama and the others in that Jan 5 meeting. Rice's memo confirms that he did not.
This is actually an almost classical application of Occam's Razor--not to be confused with Crossfire Razor.
Yesterday I heard a smart lawyer (Joe diGenova) agreeing with another smart lawyer (Andy McCarthy) that the CIA must have been spying on Flynn from overseas. Uh, why? Why would smart lawyers come up with complicated explanations of a very simple fact situation?
We know that the FBI conducts non-stop monitoring of the Russian Embassy Comms. Therefore, if Flynn communicated with the ambassador--which he did--then the FBI would inevitably capture that conversation. The Russians knew it, Flynn knew it, you and I know it. Even if the conversation had--in addition to the FBI capture--been captured in some other way, the FBI capture of the conversation would be the easiest and least controversial way to document what had happened--so you go with that!
And that's exactly what happened, as the FBI has be happy to tell the world. The FBI captured the conversation. The FBI wrote it up in "tech cuts." The FBI gave the tech cuts to James Clapper, and Clapper gave it to the White House. Boom. End of story.