NSA surveillance authorized by Congress through the Patriot Act and the FISA Amendments Act helped disrupt plots to attack the New York Stock Exchange and the New York subway system, as well as a plot to bomb a Danish newspaper that published a cartoon of the Prophet Muhammad, officials said. Intelligence officials said they will detail classified information about other thwarted attacks lawmakers soon, they said.
While the NSA is collecting phone business records, it can only query those records within specific rules set up in advance by the surveillance court, officials said. The NSA must then report those queries to the court, they said.
In 2012, the NSA ran queries on less than 300 phone numbers in a database of telephone business records, Inglis said.
While officials disputed much of the allegations Snowden made, the former contractor's disclosure of the surveillance programs could have a "long and irreversible impact on our nation's security and that of our allies," Alexander said. "The foreign intelligence programs that we're talking about are the best counterterrorism tools we have to go after these guys. We can't lose those capabilities."
Intelligence Committee Chairman Mike Rogers, a Michigan Republican, asked the officials about allegations made by Snowden.
"Is the NSA on private companies' servers?" Rogers asked.
"We are not," Alexander said.
"Does the technology exist at the NSA to flip a switch by some analyst to listen to Americans' phone calls or read their emails?" Rogers asked.
"No," Alexander said.
Still, some lawmakers said they are uncomfortable that the NSA is collecting massive amounts of phone records from U.S. carriers. The FISA court's approval for the NSA and FBI to collect huge numbers of phone records from Verizon Communications is troubling and "unprecedented," said Representative Jim Himes, a Connecticut Democrat.
Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's e-mail address is email@example.com.