Thomas Powers reviews three recent books on the American intelligence effort, in the New York Review of Books:
“Chatter” seems too casual a word for what is arguably the most important single product of the mammoth American cyber-industrial establishment which gathers “communications intelligence.” Intelligence professionals use “chatter” to describe the miscellany they acquire of the personal and operational communications of “persons of interest,” another term of art meaning people who may know or be planning something the United States wants or needs to know about.
More here.