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The Boston Globe

Nation

Surveillance thwarted terror acts, NSA chief says

Stock exchange was target of plot, House panel told

WASHINGTON — General Keith B. Alexander, the head of the National Security Agency, said Tuesday that American surveillance had helped prevent “potential terrorist events over 50 times since 9/11,” including at least 10 “homeland-based threats.” But he said that a vast majority must remain secret to avoid disclosing sources and methods.

“These programs are immensely valuable for protecting our nation and securing the security of our allies,” Alexander said at a rare public oversight hearing by the House Intelligence Committee.

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