According to the National Security Agency chief, the dozens of plots that were thwarted with the help of the government's surveillance programs included one that was directed at the New York Stock Exchange.

: General Keith Alexander, Director of the National Security Agency, testifies before the House Select Intelligence Committee

Army Gen. Keith Alexander says the NSA was monitoring an extremist in Yemen who was in contact with an individual in the United States. And by identifying that person and others, he says, the plot to bomb the stock exchange was uncovered.

The NSA director says the FBI "disrupted" the plot and arrested the suspects.

He told the House Intelligence Committee today that information from the surveillance programs had foiled some 50 terrorist plots worldwide.

Alexander and FBI deputy director Sean Joyce today also offered details of other foiled plots. Joyce said a terrorist financier inside the U.S. was identified and arrested in October of 2007, thanks to a phone record provided by the NSA.

Intelligence officials last week disclosed some details on two thwarted attacks -- one targeting the New York subway system, and one to bomb a Danish newspaper office that had published cartoon depictions of the Prophet Mohammad.

Yahoo discloses number of US govt data requests

SUNNYVALE, Calif. (AP) — Yahoo is the latest company to disclose how many requests for user data it has received from U.S. government agencies, putting the number between 12,000 and 13,000 in the six months that ended on May 31.

Yahoo Inc. CEO Marissa Mayer and General Counsel Ron Bell said in a blog post late Monday that the most common requests concerned fraud homicides, kidnappings, and other criminal investigations.

Yahoo says it plans to update the report twice a year.

Justin Sullivan/Getty Images

Internet companies have asked the U.S. government to be able to share how many requests it received related to national security and how it handled them.

Those requests were made as part of Prism, the recently revealed highly classified National Security Agency program that seizes records from Internet companies.

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