(CNN) - In a hearing Tuesday with the House Permanent Select Committee on Intelligence, the director of the National Security Agency, Keith Alexander, said that since 9/11, there have been more than 50 terror plots thwarted with the help of NSA surveillance programs.
Four of those incidents were detailed at the hearing, including thwarted plots to bomb the New York subway system and the New York Stock Exchange by linking known suspects in Pakistan and Yemen to contacts in the United States.
NSA officials are set to disclose information about the other cases in a private session with lawmakers on Wednesday.
Still, there is a debate within the intelligence community about what can be revealed to prove these programs work versus what should stay classified for fear of burning sources and methods.
Check back here for updates from the hearing.
1:06 p.m. ET –– House Intelligence Committee Chairman Mike Rogers, R-Michigan, wrapped up the hearing.
"I know this has been difficult to come and talk about very sensitive things in a public way. In order to preserve your good work and the work on behalf of all the patriots working to defend America, I still believe it was important to have a meeting where at least in some way discuss and reassure the level and oversight and redundancy of oversight on a program that we all recognize needed extra care and attention and lots of sets of eyes. I hope today in this hearing we were able to do that."
12: 40 p.m ET -
12:35 p.m. ET - Rep. Michele Bachmann, R-Minnesota, asks how damaging the leaks are.
"I think it was irreversible and significant damage to this nation," Alexander said.
"Has this helped America’s enemies?" Bachmann asked.
"I believe it has and I believe it will hurt us and our allies," he said.
12:27 p.m. ET - Rep. Jim Himes, D-Connecticut, asked how many of those 50 episodes would have been thwarted without the use of phone records. "How essential–not just contributing to–but how essential are these authorities to stop terrorist attacks?"
Glenn Greenwald, the Guardian journalist who first reported the leaks, asked a similar question on Twitter Tuesday morning.
Responding to Himes, Alexander said the surveillance programs are vital to preventing terrorism.
"Going back to 9/11, we didn't have the ability to connect the dots. This adds one more capability to help us do that," Alexander said in response. "What we're doing here, with the civil liberties and privacy oversight, does help connect the dots."
Alexander said 90% of the more than 50 plots were prevented in part because of the online surveillance–not phone records collection–of suspects overseas. "In 50%, I believe they were critical," he said. A little more than 10 of the 50 had a domestic nexus and were thus targeted using phone records.
Sean Joyce, deputy director of Federal Bureau of Investigation, also jumped in with a response to Himes.
"I think you ask an almost impossible question to say how important each dot was. What I can tell you is post 9/11, I don't recognize the FBI I came into 26 years ago. Our mission is to stop terrorism, to prevent it, not after the fact, to prevent it before it happens in the United States. I can tell you every tool is essential and vital," Joyce said. "You ask: How can you put the value on an American life? And I can tell you it's priceless."
12:20 p.m. ET - Robert S. Litt, general counsel of the Office of the Director of National Intelligence, said NSA leaker Edward Snowden "wasn't nearly as familiar with these programs as he's portrayed himself to be."
"This is what happens when somebody who sees a tiny corner of things thinks it gives him inside (understanding) into the whole program," he said.
12:01 p.m. ET - Rep. Devin Nunes, R-California, brought up other controversies plaguing the Obama administration–the IRS scandal, "Fast and Furious," Justice Department leak investigations, and the U.S. consulate attack in Benghazi–and asked NSA officials to offer assurance that the agency is not leaking information itself.
Responding, Alexander said all the information the NSA disseminates is "100% auditable" and they have "not seen one of our analysts willfully do something wrong." The only mistakes he has seen are "honest mistakes," listing a typo as an example.
Nunes further pressed officials, asking them to explain the seriousness of the leaks.
Sean Joyce, deputy director of Federal Bureau of Investigation, said they're conducting a "criminal investigation" and repeatedly described the leaks as "egregious."
"We are revealing in front of you today methods and techniques. I have told you, the examples I gave you how important they have been. The first core al Qaeda plot to attack the United States post 9-11 we used one of these programs. Another plot to bomb the New York Stock Exchange we used these programs. And now here we are talking about this in front of the world. So I think those leaks affect us," he said.
New CNN/ORC Poll: A slight majority of those questioned in the poll disapprove of the actions of the man who leaked sensitive information about the NSA program. And a similar amount say Edward Snowden, who fled to Hong Kong, should be brought back to the U.S. and prosecuted
11:36 a.m. ET - Reached by CNNMoney, the New York Stock Exchange declined to comment on the thwarted bomb plot.
11:35 a.m. ET - Asked if they plan to release the court opinions on NSA requests for phone and Internet intelligence gathering, Robert S. Litt, general counsel of the Office of the Director of National Intelligence, said they are looking into that.
11:17 a.m ET - Elaborating further on the disrupted terrorist attacks, Sean Joyce, deputy director of Federal Bureau of Investigation, said federal agencies used Internet surveillance–known as PRISM or Section 702 of the Patriot Act–to identify an extremist who was communicating with an individual in Kansas City. They were in the "very early stages" of plotting to bomb the New York Stock Exchange, he said.
Asked if their intention to bomb the NYSE was "serious," Joyce said, "The jury considered it serious since (the suspects) were all convicted."
In another instance, Joyce said they used phone records–Section 215–to identify an individual in San Diego who had "indirect contact" and who was providing financial support to an extremist outside of the United States.
11:13 a.m ET - Democratic Rep. Dutch Ruppersberger, ranking member on House Intelligence Committee, asked Alexander if he feels like the Foreign Intelligence Surveillance Court is a rubber stamp in the sense that it approves all requests from the NSA to pursue investigations.
Alexander said he does not think the court acts in such a manner and praised the the federal judges on the court as "superb," adding that they "go back and forth to make sure we do this exactly right."
11:12 a.m. ET - New CNN/ORC Poll: Just over six in ten Americans say they believe that government is so large and powerful that it threatens the rights and freedoms of ordinary Americans.
11:10 a.m. ET - House Intelligence Chairman Mike Rogers asks if the NSA has the ability to "flip a switch" and listen to Americans' phone calls or read emails
Alexander said they do not have the authority or technology to do that.
11:04 a.m. ET - Deputy Attorney General James Cole said that because of the leaks, the government runs the risk of losing its capability to operate the collection programs. He did not say why but said they won't know for several months how the leaks affected the agency's surveillance abilities.
10:57 a.m. ET - Alexander said the NSA does not unilaterally collect information from Internet companies under Section 702. The companies are compelled to provide that information by law, he said.
10:55 a.m. ET - NSA official says phone record data collected under Section 215 must be destroyed five years after acquired.
10:45 a.m. ET - Sean Joyce, deputy director of Federal Bureau of Investigation, said the surveillance programs–specifically the program that gathers intelligence from Internet companies–helped stop a plot to bomb the office of the Danish newspaper that came under heat for publishing a cartoon of Mohammed in 2006.
In the United States, the program also helped them thwart a plan to bomb the New York City subway system and a plan to bomb the New York Stock Exchange, he said.
Read the full accounts from Joyce below.
New York City subway: "In the fall of 2009, NSA using 702 authority intercepted an email from a terrorist located in Pakistan. That individual was talking with an individual located inside the United States talking about perfecting a recipe for explosives. Through legal process that individual was identified as Najibullah Zazi. He was located in Denver, Colorado. The FBI followed him to NYC. Later we executed search warrants with the NY joint terrorism task force and NYPD and found bomb making components in backpacks. Zazi later confessed to a plot to bomb the NY subway system with backpacks. Also working with FISA business records the NSA was able to provide a previously unknown number of one of the co-conspirators Adis Medunjanin. This was the first core al Qaeda plot since 9-11 directed from Pakistan."
New York Stock Exchange: "NSA utilizing 702 authority was monitoring a known extremist in Yemen. This individual was in contact with an individual in the United States named Khalid Ouazzani. Ouazzani and other individuals that we identified through a FISA that the FBI applied for through the FISC, were able to detect a nascent plotting to bomb the NYSE. Ouazzani had been providing information and support to this plot. The FBI disrupted and arrested these individuals."
Danish newspaper: "David Headley, a U.S citizen living in Chicago. The FBI received intelligence regarding his possible involvement in the 2008 Mumbai attacks responsible for the killing of over 160 people. Also, NSA through 702 coverage of an al Qaeda affiliated terrorist, found that Headley was working on a plot to bomb a Danish newspaper office that had published the cartoon depictions prophet Muhammad. In fact, Headley later confessed to personally conducting surveillance of the Danish newspaper office. He and his co-conspirators were convicted of this plot."
FBI probe: "Lastly, the FBI had opened an investigation shortly after 9-11. We did not have enough information nor did we find links to terrorism so we shortly thereafter closed the investigation. However, the NSA using the business record FISA, tipped us off that this individual had indirect contacts with a known terrorist overseas. We were able to reopen this investigation, identify additional individuals through the legal process and were able to disrupt this terrorist activity."
10:40 a.m. ET - For Section 702 of the Patriot Act, which permits the collection and surveillance of information from Internet companies, Cole said only those living outside of the United States can be targeted.
10:30 a.m .ET - Cole said that the Fourth Amendment does not apply to Section 215, the part of the Patriot Act that permits the collection of phone records.
He said people should not expect privacy on such metadata, which includes the phone numbers, the time at which phone conversations took place and the duration of those calls.
10:25 a.m. ET - Deputy Attorney General James Cole listed some of the criteria for an NSA analyst to access phone conversations. As part of the oversight process, the NSA must get permission from the Foreign Intelligence Surveillance Court.
While requesting permission, they must prove that person they want to investigate is involved with some sort of terrorist organization. To prove affiliation, the NSA must have independent evidence aside from personal writings, statements, etc, from the person they want to investigate that the individual is linked to an organization.
"You have to have additional evidence beyond that that indicates there is reasonable suspicion," he said.
Read more: House Intelligence Committee Chairman Mike Rogers said Sunday that the NSA was "not listening to" Americans' phone calls.
10:22 a.m. ET - Alexander said they will bring classified documents to Capitol Hill Wednesday that detail all 50 cases in which the NSA programs helped prevent a terror plot. As reported already on CNN, he will present two of those publicly Tuesday.
However, they will not publicly release all of the cases, saying that would give away the NSA's secrets in how it tracks suspected terrorists.
"Too much is at risk for us and our allies," he said.
Alexander described the programs as "critical" for the government's counterterrorism efforts. If they had the phone surveillance program–known as Section 215 under the Patriot Act–before the September 11, 2001 attacks, he argued, they may have been able to track phone conversations between one of the hijackers living in San Francisco and a co-conspirator in Yemen.
10:20 a.m. ET - "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 potential terrorist events over 50 times since 9-11," Alexander said.
10:19 a.m. ET - In his opening statements, Alexander said the leaked information about the phone records and Internet data sparked "considerable debate" in recent days, but the debate has been fueld by "incomplete and inaccurate information."
"Today we will provide additional detail and context on these programs to help inform that debate," he said.
10:16 a.m. ET - New CNN/ORC Poll: Americans are split on the controversial National Security Agency anti-terrorism program to record metadata on U.S. phone calls, but they support the NSA program that targets records of internet usage by people in other countries.
10:08 a.m. ET - House Intelligence Committee Chairman Mike Rogers, R-Michigan, made his opening remarks.
"I look forward to hearing from all of the witnesses about the extensive protections and oversight in place for these programs. General Alexander, we look forward to hearing what you’re able to discuss in an open forum about how the data that you obtain from providers under the Business Records provision is used; and Deputy Attorney General Cole, we look forward to hearing more about the legal authorities themselves, and the state of the law on what privacy protections Americans’ have in business records," he said, according to his prepared remarks.
"General Alexander, you and I have talked over the past week about the need to be able to publicly elaborate on the success stories these authorities have contributed to without jeopardizing ongoing operations," he added. "I place the utmost value in protecting sources and methods, but I also recognize that when we are forced into the position of having to publicly discuss intelligence programs due to irresponsible, criminal behavior that we also have to carefully balance the need for secrecy with educating the public."