Senate Intelligence Committee Chairman Dianne Feinstein discusses reports that the NSA has been keeping records of cellular phone numbers.

A secret National Security Agency program to collect vast amounts of phone records has foiled multiple attempted terrorist attacks inside the United States, the chair of the Senate Intelligence Committee told reporters on Thursday.

Sen. Dianne Feinstein did not specify how many attempted attacks had been prevented, or the nature of the threats, but the California Democrat said there had been more than one.

The remarks were made to reporters following a meeting with senators who were concerned over a report in a British newspaper that the NSA had requested phone records from a division of telecommunications giant Verizon. According to Feinstein, 27 senators attended the meeting and voiced concerns about the policy.

"We are always open to changes. But that doesn't mean there will be any. It does mean that we will look at any ideas, any thoughts, and we do this on everything," she said.

Earlier in the day Feinstein defended the surveillance as a legal and long-standing government program.

“It began in 2009 – what appeared in the Guardian today, as I understand it, is simply a court reauthorization of a program. The court is required to look at it every three months,” she said.

And while Republican Senator Rand Paul called the surveillance of Verizon phone records described in the report “an astounding assault on the constitution,” other GOP lawmakers including Senator Lindsey Graham disagreed.

“I have no problem. I am a Verizon customer. You can have my phone number, and put it in a database,” Graham said. “If they get a hit between me and some guy from Waziristan,” officials should investigate, he said.

House Speaker John Boehner said President Obama should “explain to the American people why the administration considers this a critical tool in protecting our nation from the threats of a terrorist attack.”

The practice was first revealed by the British newspaper The Guardian on Wednesday, which obtained and published a highly classified court order that requires the production of “telephony metadata” by the telecommunications giant.

Sen. Lindsey Graham addresses Attorney General Eric Holder Thursday over a recent report that the NSA is collecting people's Verizon phone numbers.

The order, marked "Top Secret" and issued by the U.S. Foreign Intelligence Surveillance Court, instructs Verizon Business Network Services, a subsidiary that provides internet and telecommunications services for corporations, to hand over data including all calling records on an "ongoing, daily basis.”

“On its face, the order reprinted in the article does not allow the government to listen in on anyone’s telephone calls,” the official said.

The NSA, Department of Justice, and Federal Bureau of Investigation have issued no formal comment on the report or purported practices described in it.

While declining to say how long the particular order referenced in the Guardian article has been in place, White House spokesman Josh Earnest said that a “robust legal regime” reviews government powers under the Patriot Act “to ensure that they comply with the Constitution.”

“This strict regime reflects the president’s desire to strike the right balance between protecting our national security and protecting constitutional rights and civil liberties,” Earnest said.

Attorney General Eric Holder said he could not discuss the report regarding NSA information gathering today while appearing in a previously scheduled open budget hearing. Members of Congress have been “fully briefed” on the issue, he said.

Senate Majority Leader Harry Reid urged caution, saying the program “isn’t anything that’s brand new.”

“It’s gone on for some 7 years,” Reid said. “We’ve tried often to make it better and make it work.”

Signed by Judge Roger Vinson of the U.S. Foreign Intelligence Surveillance Court in April, the order requires the “production of certain call detail records,” and is set to expire on the evening of July 19, 2013. The order pertains to information including the phone numbers making and receiving the call, as well as the time the call was made and how long it lasts. It does not include the “name, address, or financial information of a subscriber or customer,” according to the order.

The order “does not require Verizon to produce telephony metadata for communications wholly originating and terminating in foreign countries,” according to the document.

Earlier on Wednesday, an Obama administration official defended the policy of gathering phone records from American citizens while neither confirming nor denying a report that the National Security Agency is collecting information regarding communications by Verizon customers.

Such information has been “a critical tool in protecting the nation from terrorist threats,” the senior Obama administration official said.

Getty Images file This undated photo provided by the National Security Agency (NSA) shows its headquarters in Fort Meade, Maryland.

While not confirming any particulars of the report, the administration official said that data such as that described in the article “allows counterterrorism personnel to discover whether known or suspected terrorists have been in contact with other persons who may be engaged in terrorist activities, particularly people located inside the United States.”

Verizon said it had no comment Wednesday on the accuracy of the story published by the Guardian or the document the report was based on, the company’s chief counsel Randy Milch said in note sent to the company’s employees.

“Verizon continually takes steps to safeguard its customers’ privacy,” Milch said in the note. “Nevertheless, the law authorizes the federal courts to order a company to provide information in certain circumstances, and if Verizon were to receive such an order, we would be required to comply.”

The disclosure of the order, which has not been independently verified by NBC News, comes after the Obama administration has taken fire for a Justice Department subpoena of Associated Press phone records.

Holder told NBC News Wednesday that he has no intention of stepping down from his job despite calls by some congressional Republicans for his resignation, citing the AP seizure.

Senator Jeff Merkley, a Democrat from Oregon, called the collection of call data as described in the Guardian report “an outrageous breach of Americans’ privacy” in a news release Thursday. “This bulk data collection is being done under interpretations of the law that have been kept secret from the public. Significant FISA [Foreign Intelligence Surveillance Act] court opinions that determine the scope of our laws should be declassified.”

Verizon had 98.9 million wireless customers at the end of the first quarter this year, according to an earnings report released in April, as well as about 11.7 million residential and 10 million commercial lines. It is not clear whether other parts of Verizon might have received similar orders. The order explicitly prohibits any person from disclosing that the NSA or FBI Investigation has sought records under the order.

“Now that this unconstitutional surveillance effort has been revealed, the government should end it and disclose its full scope, and Congress should initiate an investigation,” Michelle Richardson, legislative counsel for the American Civil Liberties Union, said in a statement. “This disclosure also highlights the growing gap between the public’s and the government’s understandings of the many sweeping surveillance authorities enacted by Congress.”

The law on which the order explicitly relies is the "business records" provision of the USA Patriot Act.

Senators Ron Wyden of Oregon and Mark Udall of Colorado, both Democrats on the Senate Intelligence Committee, said in a March 2012 letter to Attorney General Eric Holder that most Americans would “stunned to learn the details of how these secret court opinions have interpreted section 215 of the Patriot Act.”

“As we see it, there is now a significant gap between what most Americans think the law allows and what the government secretly claims the law allows,” the senators wrote in the letter. “This is a problem, because it is impossible to have an informed public debate about what the law should say when the public doesn’t know what its government thinks the law says.”

Former vice president Al Gore called the practices described in the order “obscenely outrageous” in a message posted on Twitter Wednesday night. “In digital era, privacy must be a priority,” Gore wrote. “Is it just me, or is secret blanket surveillance obscenely outrageous.”

The order is the first concrete evidence that U.S. intelligence officials are continuing a broad campaign of domestic surveillance that began under President George W. Bush and caused great controversy when it was first exposed, according to Reuters.

NBC News' Chuck Todd, Peter Alexander, Andrew Rafferty Alastair Jamieson and the Associated Press contributed to this report.

Related:

This story was originally published on