James Angleton was convinced there was a mole leaking intelligence information to Russia. Since at the time, only a handful of people in Washington received intelligence reports, Angleton had an idea. He would place different identifiers in each report so that on the surface, all of the intelligence reports appeared to be identical when in fact, they weren't. Then Angleton checked with his source in Russia and found the person leaking the information and that person was JFK. Yes, there were a lot of people mad at JFK. We've all seen the list...the mob, big oil, military-industrial, Hoover, Dulles, etc...but JFK was seen as a national security risk when it was apparent he was leaking US intelligence.