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Fort Meade, UNITED STATES:  The logo of the National Security Agency (NSA) hangs at the Threat Operations Center inside the NSA in the Washington suburb of Fort Meade, Maryland, 25 January 2006. US President George W. Bush delivered a speech behind closed doors and met with employees in advance of Senate hearings on the much-criticized domestic surveillance.   AFP PHOTO/Paul J. RICHARDS  (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images)
Fort Meade, UNITED STATES:  The logo of the National Security Agency (NSA) hangs at the Threat Operations Center inside the NSA in the Washington suburb of Fort Meade, Maryland, 25 January 2006. US President George W. Bush delivered a speech behind closed doors and met with employees in advance of Senate hearings on the much-criticized domestic surveillance.   AFP PHOTO/Paul J. RICHARDS  (Photo credit should read PAUL J. RICHARDS/AFP/Getty Images)

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How terrorists shifted communications

Counterterrorism expert Matt Olsen says knowledge of NSA tactics changed the way terrorists communicate.

How terrorists shifted communications

Counterterrorism expert Matt Olsen says knowledge of NSA tactics changed the way terrorists communicate.