The process starts on the intelligence-gathering side, where a tremendous flood of information pours into the National Counterterrorism Center, a clearinghouse agency created after the Sept. 11, 2001, attacks and run by the director of national intelligence.

NPR: 'System Failure' In U.S. Screening For Terrorists

They fired off a memo under the longwinded title, "How Best to Express the Department's Privacy and Civil Liberties Concerns over Draft Guidelines Proposed by the Office of the Director of National Intelligence and the National Counterterrorism Center, " according to an email obtained through the Freedom of Information Act.

WSJ: U.S. Terrorism Agency to Tap a Vast Database of Citizens