Greenwald pushes back against NSA

General Keith Alexander, Director of the National Security Agency, listens during a hearing of the Senate Judiciary on Capitol Hill October 2, 2013 in Washington, DC.
General Keith Alexander, Director of the National Security Agency, listens during a hearing of the Senate Judiciary on Capitol Hill October 2, 2013 in Washington, DC.

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    Greenwald pushes back against NSA

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CNN's Christiane Amanpour speaks with Glenn Greenwald about the U.S. intelligence chiefs' testimony before Congress.