When pressed by the House Intelligence Committee today, National Security Agency head General Keith Alexander revealed that surveillance programs that have recently come to light helped stop over 10 domestic terrorist plots and more than 50 worldwide since 9/11.

The Guardian’s liveblog of the hearing (via Ars Technica) noted the comments, which can also be watched on CSPAN’s website.

Opinions will be divided about whether stopping 10 domestic threats was worth the tradeoff in privacy. At less than one a year, that’s a lot of monitoring to find each plot. There’s also no information on the size of these plots. Still, the information gathered presumably helped to save lives by providing early warning of planned terrorist actions, so that’s a tough equation to compute.

A Deputy Director at the FBI recently claimed that NSA monitoring helped the agency to thwart a bomb plot on the New York Stock Exchange and New York City subway.

During Tuesday’s hearing, NSA Deputy Director Jon Chris Inglis also revealed that about 22 people (20 analysts and two supervisors) are able to sign off on targeting US-based phone conversations.

As for how many government contractors there are in positions similar to whistleblower Edward Snowden, Alexander admitted they are “on the order of a thousand.”

Earlier today, Google filed a petition to be more transparent with disclosing national security and FISA requests it receives, citing its first amendment freedom of speech rights.

See also: NSA update: Here’s the latest on the raucous surveillance scandal

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