The House Intelligence Committee held a hearing today about the NSA's covert surveillance programs, and to demonstrate just how tough-minded they planned to be, here's what they called it:
How Disclosed N.S.A. Programs Protect Americans, and Why Disclosure Aids Our Adversaries
Fair and balanced! NSA's director testified that domestic surveillance had helped prevent over 50 "potential terrorist events":
In addition, the deputy director of the Federal Bureau of Investigation, Sean Joyce, listed two newly disclosed cases that have now been declassified in an effort to respond to the leaking of classified information about surveillance by Edward J. Snowden, a former N.S.A. contractor.
Mr. Joyce described a plot to blow up the New York Stock Exchange by a Kansas City man, whom the agency was able to identify because he was in contact with “an extremist” in Yemen who was under surveillance. Mr. Joyce also talked about a San Diego man who planned to send financial support to a terrorist group in Somalia, and who was identified because the N.S.A. flagged his phone number as suspicious through its database of all domestic phone call logs, which was brought to light by Mr. Snowden’s disclosures.
The Kansas City man is Khalid Ouazzani, who, as part of a plea bargain in 2010, admitted that he sent money to Al Qaeda. He was never charged with planning any attacks inside the United States, and the NYSE bombing was described as "nascent plotting," so it's hard to know just how serious this was. Still, at least Ouazzani actually did something. The San Diego man merely planned to send money.
So far, the government's examples of terrorist plots prevented by the NSA's surveillance programs have been pretty thin. Aside from these two, they've also taken credit for stopping David Headley and Najibullah Zazi. But Headley scouted locations for the 2008 Mumbai bombing, which was successful. So no points there, though NSA might have prevented Headley from doing further damage. As for Zazi, he was indeed planning suicide bombings on the New York subway, but it's unclear just how instrumental NSA surveillance really was in catching him.
None of this is to say that NSA's claims are false or that their surveillance programs are ineffective. But most of their claims are unverified, and the few they've made public appear to have been exaggerated. So take this all with a grain of salt.