Why Congress is fighting over a central tool of American surveillance

A computer workstation bears the National Security Agency logo inside the Threat Operations Center in the Washington suburb of Fort Meade, Md.

Section 702 of the Foreign Intelligence Surveillance Act is responsible for a huge share of intel collected by the U.S. Lawmakers and civil liberties advocates are worried it enables warrantless spying on U.S. citizens.

(Image credit: Paul J. Richards)