He said the surveillance programs were critical to unraveling terrorist plots at home and abroad. In particular, he cited the cases of Najibullah Zazi, an Afghan American who pleaded guilty to planning suicide attacks in New York, and Pakistani American David C. Headley, who was arrested in 2009 for his role in a terrorist attack the year before in Mumbai, and who was plotting to attack a Danish newspaper that published a satirical cartoon of the prophet Muhammad.
“I think what we’re doing to protect American citizens here is the right thing,’’ Alexander said under sometimes hostile questioning before the Senate Appropriations Committee. “Our agency takes great pride in protecting this nation and our civil liberties and privacy.’’
Alexander’s appearance featured the unusual spectacle of the head of the ultra-secretive NSA publicly discussing highly classified programs as the administration is pursuing possible criminal charges against a former NSA contractor who says he leaked the details of those efforts.
Alexander’s words reflected the intense debate consuming Washington since last week’s revelations that the government has been collecting the call records of millions of Americans and scooping up e-mail and other user records of foreign targets from nine leading technology companies, including Google, Facebook and Microsoft.
The confessed leaker, Edward Snowden, 29, surfaced publicly again Wednesday, saying that the United States has mounted massive hacking operations against hundreds of Chinese targets since 2009 as part of a global campaign. Snowden, in an interview in Hong Kong, vowed to fight the U.S. government in the courts if it attempts to extradite and prosecute him.
U.S. officials said criminal charges are being prepared against Snowden, but they declined to specify the nature of the charges or when they might be filed. The officials spoke on the condition of anonymity to discuss ongoing deliberations.
The Obama administration has defended its extensive surveillance, and President Obama has said he welcomes a public debate about the programs. Alexander followed up on that pledge Wednesday, vowing to quickly make public data showing the phone program has prevented attacks.
“Over the next week, it will be our intent to get those figures out. . . . I want the American people to know we’re being transparent here,’’ he said.
The phone-records program, disclosed last week by Britain’s Guardian newspaper, collects customer “metadata,” including the phone numbers dialed and the length of calls — and, senators said, location data, which intelligence analysts use to detect patterns and personal connections. The administration said that the program does not monitor the content of calls and that it has been reviewed by a secret surveillance court and Congress.
A separate Internet surveillance program, known as PRISM, allows the NSA to collect videos, photos, e-mails, documents and connection logs for foreign users thought to be located overseas through nine leading Internet companies. The government obtains the data through orders approved by the secret court established by the Foreign Intelligence Surveillance Act. That program was disclosed by The Washington Post and the Guardian.
Alexander appeared at a hearing to discuss cybersecurity spending, but some committee members took the opportunity to question him about the surveillance programs.
The four-star Army general said he thinks the leaks have hurt national security. But he said it is important to allay concerns across the political spectrum that the government surveillance was exceeding constitutional bounds.
“Grave harm has already been done by opening this up,” he said. “There is no doubt in my mind that we will lose capabilities as a result of this, and that not only the United States but those allies that we would help will no longer be as safe as they were two weeks ago.”
But, he said, he wanted to counter perceptions the agency was violating privacy. “If the perspective is we’re trying to hide something because we did something wrong, we’re not,” he said.
Senators pressed Alexander on how Snowden, a fairly low-level contract employee doing computer systems work, could have had access to so much classified information.
“How on Earth does this happen?” asked Sen. Jon Tester (D-Mont.).
Acknowleging “grave concerns” about Snowden’s apparently extensive access to highly sensitive data, Alexander replied: “In this case, this individual was a system administrator with access to key parts of the network. That is of serious concern to us and something that we have to fix.”
The Office of the Director of National Intelligence has ordered a damage assessment following Snowden’s disclosures. A senior intelligence official said Wednesday that the CIA also has opened an internal investigation to determine what activities Snowden was involved in when he worked there.
“Obviously, Mr. Snowden’s actions over the past week-plus are generating a lot of activity on the part of the intelligence community and the CIA,” said the official, who spoke on the condition of anonymity to discuss an ongoing inquiry.
CIA officials could not say exactly when he worked there. After leaving the agency, he worked for the technology company Dell and later for Booz Allen Hamilton, the consulting firm. While working for Booz Allen this year, he was assigned to the NSA’s Threat Operations Center in Honolulu, where he is believed to have downloaded highly classified material.
Under questioning from Sen. Patrick J. Leahy (D-Vt.), Alexander said the PRISM program was critical to developing the key lead in the Zazi case. He said the program turned up information from operatives overseas, which led to connections to an unidentified person in Colorado. That data was passed to the FBI, which determined the person was Zazi, he said.
From there, the phone records program was used to “find out connections from Zazi to other players throughout communities, specifically in New York City,’’ Alexander said.
He said that the PRISM program helped develop information that led to Headley and that the phone records program provided “corroborating” evidence.
“These authorities complement each other in helping us identify different terrorist actions and help disrupt them,” he said. “The reality is they work together.”
Alexander seemed to suggest that current surveillance programs might have helped prevent the attacks of Sept. 11, 2001. He said that one of the attackers was picked up in telephone intercepts but that officials did not have the data to make the right connections before the attacks.
In interviews with The Post and the Guardian last week, Snowden said that he was motivated by what he considered a widespread invasion of privacy by the NSA. In Hong Kong, where he has been hiding, he added that the United States has engaged in a worldwide hacking campaign.
The South China Morning Post, which said it interviewed Snowden at an undisclosed location in Hong Kong, said he presented “unverified documents” describing an extensive U.S. campaign to obtain information from computers in Hong Kong and mainland China.
“We hack network backbones — like huge Internet routers, basically — that give us access to the communications of hundreds of thousands of computers without having to hack every single one,” he told the newspaper.
According to Snowden, the NSA has engaged in more than 61,000 hacking operations worldwide, including hundreds aimed at Chinese universities, businesses and public officials.
Senior American officials have accused China of hacking into U.S. military and business computers. Snowden’s claims of extensive U.S. hacking of Chinese computers track assertions made repeatedly by senior Chinese government officials that they are victims of similar cyber-intrusions.
Snowden’s assertions could not be verified, and U.S. officials did not respond to requests for comment.
It is unclear what step the U.S. government will take against Snowden, although it seems likely that he will face criminal charges. Kenneth L. Wainstein, a former assistant attorney general for national security, said the Justice Department has no choice except to prosecute him.
“The fact that you might have altruistic views doesn’t give you license to unilaterally decide to disclose government secrets and possibly cause grave damage to the government’s counterterrorism operations,” he said in an interview.
Jia Lynn Yang in Hong Kong and Karen DeYoung and Julie Tate in Washington contributed to this report.