Eager to quell a domestic furore over U.S. spying, the nation’s top intelligence official stressed on Saturday that a previously undisclosed programme for tapping into Internet usage was authorized by Congress, falls under strict supervision of a secret court and cannot intentionally target a U.S. citizen. He decried the revelation of that and another intelligence-gathering program as reckless.

For the second time in three days, Director of National Intelligence James Clapper took the rare step of de-classifying some details of an intelligence program to respond to media reports about counterterrorism techniques employed by the government.

“Disclosing information about the specific methods the government uses to collect communications can obviously give our enemies a ‘playbook’ of how to avoid detection,” he said in a statement.

Mr. Clapper said the data collection under the programme, first unveiled by the newspapers The Washington Post and The Guardian in Britain, was conducted with the approval of the secret Foreign Intelligence Surveillance Act Court and with the knowledge of Internet service providers. He emphasized that the government does not act unilaterally to obtain that data from the servers of those providers.

Mr. Clapper’s reaction came a day after President Barack Obama defended the counterterrorism methods and said Americans need to “make some choices” in balancing privacy and security.

Mr. Clapper said that under that court-supervised programme, only a small fraction of the records collected ever get examined because most are unrelated to any inquiries into terrorism activities.

Mr. Clapper said the programme, authorized in the USA Patriot Act, has been in place since 2008, the last year of the George W. Bush administration, and “has proven vital to keeping the nation and our allies safe.

“It continues to be one of our most important tools for the protection of the nation’s security,” he said.

Among the previously classified information about the Internet data collection that Mr. Clapper revealed —

It is an internal government computer system that allows the government to collect foreign intelligence information from electronic communication service providers under court supervision.

The government does not unilaterally obtain information from the servers of U.S. electronic communication service providers. It requires approval from a FISA Court judge and is conducted with the knowledge of the provider and service providers supply information when they are legally required to do so.

The programme seeks foreign intelligence information concerning foreign targets located outside the United States.

The government cannot target anyone under the program unless there is an “appropriate, and documented, foreign intelligence purpose” for the acquisition. Those purposes include prevention of terrorism, hostile cyber activities or nuclear proliferation. The foreign target must be reasonably believed to be outside the United States. It cannot intentionally target any U.S. citizen or any person known to be in the U.S.

The dissemination of information “incidentally intercepted” about a U.S. person is prohibited unless it is “necessary to understand foreign intelligence or assess its importance, is evidence of a crime, or indicates a threat of death or serious bodily harm.

The Post and the Guardian cited confidential slides and other documents about PRISM for their reports. They named Google, Facebook, Microsoft Corp., Apple Inc., Yahoo Inc., AOL Inc. and Paltalk as companies whose data has been obtained.

All the companies have issued statements asserting that they aren’t voluntarily handing over user data. They also are emphatically rejecting newspaper reports indicating that PRISM has opened a door for the NSA to tap directly on the companies’ data centers whenever the government pleases.

In his statement, Mr. Clapper appeared to support that claim by stressing that the government did not act unilaterally, but with court authority.

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