Intelligence officials defended the National Security Agency's sweeping surveillance of millions of Americans during a House committee hearing on Tuesday, arguing that government spying has helped thwart over 50 "potential terrorist events" since the Sept. 11, 2001 attacks.

"I would much rather be here today debating this than explaining why we were unable to prevent another 9/11 [attack]," declared NSA Director Keith Alexander before the House Intelligence Committee, reports USA Today.

The NSA's controversial program has come under fire since Edward Snowden, a former CIA agent, leaked documents revealing that the government is secretly monitoring Americans' phone logs by working with companies like Verizon and AT&T. In addition, the NSA's PRISM program has tapped into the Internet servers of major companies like Facebook and Google.

In testimony, officials announced that the program was used to foil a terror plot to blow up the New York Stock Exchange in addition to a case in which a man was aiding a terrorist group overseas.

"In recent years, these programs, together with other intelligence, have protected the U.S. and our allies from terrorist threats across the globe to include helping prevent the terrorist - the potential terrorist events over 50 times since 9/11," Alexander stated, the Washington Post reports.

He said at least 10 of the plots targeted the United States.

FBI Deputy Director Sean Joyce added that a provision in the Foreign Intelligence Surveillance Act helped officials monitor a "known extremist in Yemen" who was in contact with an individual in the United States. The information led to disruption of the New York Stock Exchange plot, Joyce said.

Joyce also said that the use of a FISA business record provision helped officials with an investigation involving an individual who was communicating with an overseas terrorist.

"The NSA, using the business record FISA, tipped us off that this individual had indirect contacts with a known terrorist overseas," said Joyce. "We were able to reopen this investigation, identify additional individuals through a legal process and were able to disrupt this terrorist activity."

"So that's four cases total that we have put out publicly," Alexander said Tuesday.

Alexander said he would provide details of the 50 examples he cited to lawmakers in private on Wednesday.