Senate Panel Presses N.S.A. on Phone Logs

At a Senate Judiciary Committee hearing, the chairman, Patrick J. Leahy, Democrat of Vermont, accused Obama administration officials of overstating the success of the domestic call log program. He said he had been shown a classified list of “terrorist events” detected through surveillance, and it did not show that “dozens or even several terrorist plots” had been thwarted by the domestic program.

“If this program is not effective it has to end. So far, I’m not convinced by what I’ve seen,” Mr. Leahy said, citing the “massive privacy implications” of keeping records of every American’s domestic calls.

At the start of the hearing, the Obama administration released previously classified documents outlining the rules for how the domestic phone records may be accessed and used by intelligence analysts. And as senators debated the program, The Guardian published on its Web site a still-classified 32-page presentation, apparently downloaded by Edward J. Snowden, the former N.S.A. contractor, that describes a separate surveillance activity by the agency.

Called the XKeyscore program, it apparently gives N.S.A. analysts access to virtually any Internet browsing activity around the world, data that is being vacuumed up from 150 foreign sites.

Together, the new disclosures provided additional details on the scope of the United States government’s secret surveillance programs, which have been dragged into public view and public debate by leaks from Mr. Snowden, who remains stranded in a Moscow airport.

The hearing came a week after the House voted narrowly to defeat an amendment to shut down the N.S.A.’s domestic phone record tracking program. The 217-to-205 vote was far closer than expected, and it — along with shifting poll numbers — suggested that momentum against the domestic program was building. In recent days even some of the most outspoken supporters of the program have said they are open to adjusting it.

The Obama administration has been trying to build public support for its surveillance programs, which trace back to the Bush administration, by arguing that they are subject to strict safeguards and court oversight and that they have helped thwart as many as 54 terrorist events. That figure, Mr. Leahy emphasized, relies upon conflating another program that allows surveillance targeted at noncitizens abroad, which has apparently been quite valuable, with the domestic one.

Still, Senator Dianne Feinstein, the California Democrat who is chairwoman of the Senate Intelligence Committee, said she supported overhauling the program but keeping it in place because it generates information that might prevent attacks.

John C. Inglis, the deputy director of the N.S.A., said there had been 13 investigations in which the domestic call tracking program made a “contribution.” He cited two discoveries: that several men in San Diego were sending money to a terrorist group in Somalia, and that a suspect who was already under scrutiny in a subway bomb plot was using a different phone.

Robert S. Litt, the top lawyer in the Office of the Director of National Intelligence, testified that the Obama administration was also “open to re-evaluating this program” to create greater public confidence that it protects privacy while “preserving the essence of the program.” Administration officials have emphasized that the program collects only so-called metadata, and not the contents of phone calls.

Still, the top Republican on the committee, Senator Charles E. Grassley of Iowa, asked skeptical questions about the legal basis for the program while criticizing the director of national intelligence, James Clapper, for making inaccurate statements to Congress about it in March. Mr. Clapper has since apologized.

“Nothing can excuse this kind of behavior from a senior administration official of any administration, especially on matters of such grave importance,” Mr. Grassley said.

A series of slides describing XKeyscore, dated 2008, make it clear that the security agency system is collecting a huge amount of data on Internet activity around the globe, from chats on social networks to browsing of Web sites and searches on Google Maps. The volume of data is so vast that most of it is stored for only three days, although metadata — information showing logins and server activity, but not content — is stored for a month. Several of the pages were redacted by The Guardian.

Some of the servers the agency uses are run by foreign intelligence services of friendly nations, including Britain, Australia, Canada and New Zealand, but other servers may be on the soil of countries unaware the agency is mining Internet “pipes” on their soil. Some of the harvesting of data takes place on the coasts of the United States, and along the Mexican border. Most sites are in Europe, the Middle East, and along the borders of India, Pakistan, and China.