(Washington, USA) - The United States has launched a criminal investigation and is taking "all necessary steps" to prosecute Edward Snowden for exposing secret US surveillance programs, the FBI director said Thursday.
Robert Mueller, who is to step down soon after more than a decade leading the Federal Bureau of Investigation, defended the Internet and phone sweeps as vital tools that could have prevented the attacks of September 11, 2001.
"These disclosures have caused significant harm to our nation and to our safety," Mueller told lawmakers at a hearing of the House Judiciary Committee.
"As to the individual who has admitted to making these disclosures, he is the subject of an ongoing criminal investigation," he said. "We are taking all necessary steps to hold the person responsible for these disclosures."
The FBI chief's comments were the first explicit confirmation that the US government was pursuing Snowden, the 29-year-old American IT specialist who has admitted to leaking information about far-reaching surveillance programs.
Snowden, who worked as a subcontractor handling computer networks for the National Security Agency (NSA), is in Hong Kong, a semi-autonomous Chinese territory, where he has vowed to contest any possible extradition in court.
Mueller defended the collection of American phone records and of Internet data related to foreign targets, which officials maintain were legal programs approved by federal judges and in accordance with the Constitution.
"The program is set up for a very limited purpose and a limited objective, and that is to identify individuals in the United States who are using a telephone for terrorist activities and to draw that network," he said.
Mueller told lawmakers that one of the 9/11 hijackers, Khalid al-Mihdhar, had made phone calls from San Diego to a known Al-Qaeda safe house in Yemen.
"If we had had this program in place at the time, we would have been able to identify that particular telephone number in San Diego," Mueller said.
"If we had the telephone number from Yemen we would have matched up to that telephone number in San Diego, got further legal process, identified al-Mihdhar."
Many lawmakers remained skeptical, however. Democrat John Conyers expressed alarm at the scale and secrecy of the surveillance programs, saying: "It's my fear we are on the verge of becoming a surveillance state."
General Keith Alexander, the head of the National Security Agency, told lawmakers on Wednesday that "dozens" of terror attacks had been thwarted by programs and that the leaks had caused "great harm" to national security.
On Monday the NSA will release the specific number of attacks prevented, said Senator Dianne Feinstein, the chair of the Senate intelligence committee.
Some lawmakers opposed to the domestic surveillance techniques have demanded proof that the data collection yielded concrete results.
Snowden, a technician working for a private contractor and assigned to an NSA base in Hawaii, surfaced over the weekend in Hong Kong to give media interviews.
In addition to disclosing the NSA's acquisition of phone logs and data from nine Internet giants -- including Google, Microsoft and Facebook -- Snowden also described secret global hacking operations, some targeting China.
Snowden told the South China Morning Post there had been more than 61,000 NSA hacking operations globally, targeting powerful "network backbones" that can yield access to hundreds of thousands of individual computers.
There were hundreds of targets in mainland China and Hong Kong, he was quoted as saying by the Hong Kong daily.
Snowden said his revelations had exposed "the hypocrisy of the US government when it claims that it does not target civilian infrastructure."
The US administration has said that while the NSA did gather large quantities of telephone metadata, it could not mine the logs to target a specific user without authorization from a secret court.
And it has said the Internet monitoring program did not target Americans or even foreigners on US soil.
China has said little about the case, and foreign ministry spokeswoman Hua Chunying on Thursday dodged questions about whether Washington had sought Snowden's extradition and how China would react if he applied for asylum.
China's state media has also remained relatively quiet on the case, but the government-owned China Daily said on Thursday that news of the US program "is certain to stain Washington's overseas image and test developing Sino-US ties."
"How the case is handled could pose a challenge to the burgeoning goodwill between Beijing and Washington given that Snowden is in Chinese territory and the Sino-US relationship is constantly soured on cybersecurity," it said.
US officials have accused China of state-sponsored hacking targeting the military, infrastructure and corporations, charges denied by Beijing, which insists China is itself the target of considerable foreign cyberattacks.
