Tuesday FBI Deputy Director Sean Joyce said the NSA’s surveillance program helped stop an attack on the New York Stock Exchange. (The Washington Post)

In testimony before Congress Tuesday, senior intelligence and law enforcement officials said recently revealed surveillance programs have disrupted more than 50 “potential terrorist events,” including at least 10 plots that were based inside the United States. Four of those cases have been made public. Sean Joyce, deputy director of the FBI, listed them in this order:

2009: According to Joyce, the now-public surveillance program called PRISM, helped locate Afghan-American Najibullah Zazi and stop his plan to bomb the New York City subway system. The NSA intercepted e-mail between Zazi and a terrorist located in Pakistan that contained recipes for explosives. After Zazi’s identity and location were determined through a legal process, he was followed to New York City where an execution of a search warrant revealed bomb ingredients in his backpacks. Zazi later confessed to the plot, was convicted and sentenced to life in prison. Using FISA business records, the NSA also found co-conspirator Adis Medunjanin. “This was the first core al-Qaida plot since 9/11 directed from Pakistan,” said Joyce.

2010: Similar surveillance picked up conversation between a “known extremist in Yemen” and Moroccan-born naturalized U.S. citizen, Khalid Ouazzani. From these interactions, the FBI detected a “nascent plotting” to bomb the New York Stock Exchange. Ouazzani provided information and funds to support these efforts before the FBI disrupted the plans and arrested him and his co-conspirators. In 2010, Ouazzani pled guilty to supporting a terrorist organization, bank fraud and overseas money laundering. His co-conspirators also pled guilty to terrorism charges in federal court. Ouazzani is awaiting sentencing.

2009: The FBI received intelligence regarding a U.S. citizen’s involvement in the 2008 Mumbai attacks that killed over 160 people. The NSA also found information that the same citizen was working on a plot to bomb a Danish newspaper office that had published cartoons of the Prophet Mohammed. The citizen was identified as David Headley, a resident of Chicago. He was arrested at O’Hare International Airport before a flight to Pakistan and his co-conspirators were also convicted. Afterwards, Headley confessed to helping plan the Mumbai attacks and surveillance of the Danish newspaper office. In January 2013, he was sentenced to 35 years in prison.

2001: The FBI became aware of a San Diego man’s links to terrorism shortly after the Sept. 11 terror attacks, but did not have enough information to continue an investigation. After the NSA found “indirect contacts” between the man and a known terrorist group overseas, apparently al-Shabab in Somalia, it reopened the investigation and was able to stop the man from financing al-Shabab. Joyce did not specifically identify the case, but it appears to have led to the successful prosecution of four Somali immigrants this year.