The National Security Agency last year checked fewer than 300 telephone numbers against its database containing details about every phone call made in America, intelligence officials said Tuesday.
The rare admission was part of the Obama administration’s effort to reassure Americans about NSA data-gathering programs that officials said had foiled more than 50 terrorist plots in the United States and abroad.
“In recent years, the information gathered from these programs provided the U.S. government with critical leads to help prevent over 50 potential terrorist events in more than 20 countries around the world,” including 10 in the U.S., Army Gen. Keith B. Alexander, the NSA’s director, told lawmakers Tuesday.
The freshly declassified figures were announced at an unprecedented public hearing of the House Permanent Select Committee on Intelligence about the two NSA programs exposed this month by self-proclaimed whistleblower Edward Snowden, a former NSA contractor.
He said that more than 1,000 computer systems administrators at the NSA have the kind of access to the agency’s intranet that Mr. Snowden apparently exploited. Most of them, like Mr. Snowden, are contract employees.
Deputy NSA Director Christopher Inglis said that one program exposed by Mr. Snowden, code-named Prism, collects email, text, video messages and other online communications from nine Internet companies, but it is used only to target foreigners believed to be outside the United States.
The other program, authorized under the USA Patriot Act, involves the collection of “metadata” from about every telephone call made or received in the United States, Mr. Inglis said.
But the agency is not recording “the content of any communications, what you’re saying during the course of the conversation, the identities of the people that are talking or any cellphone locational information,” he added. Instead, the NSA collects only the numbers called and calling, so that when the agency discovers the telephone number of a terrorist overseas, it can be discovered whether that person had been in touch with anyone in the United States.
“The controls on the use of this data at NSA are specific, rigorous and designed to ensure focus on counterterrorism,” Mr. Inglis said. “To that end, the metadata acquired and stored under this program may be queried only [under] a reasonable articulable suspicion” of a link to terrorism.
Only 22 people in the entire NSA were empowered to certify that such a suspicion existed, Mr. Inglis testified, and they did so last year in regard to fewer than 300 phone numbers, called “selectors” when they are applied to the database.
“The reason there were so few selectors approved is that the [Foreign Intelligence Surveillance] court has determined that there is a very narrow purpose for this use,” he said, adding it is only for uncovering links of suspected terrorists in the United States.
A separate court order is not required for each query, he said.
“The court explicitly approves the process by which those determinations [to search for phone numbers] are made,” Mr. Inglis said, “and the Department of Justice now provides a rich oversight auditing of that capability.”