The U.S. National Security Agency has halted a form of surveillance that allowed it to collect without a warrant the digital communications of Americans that mentioned a foreign intelligence target, the spy agency confirmed on Friday.
The decision to stop the once-secret activity, which collected messages sent to or received from people believed to be living overseas, arrives as a sudden and unexpected triumph for privacy advocates who were long critical of the program, which U.S. officials had defended as both lawful and important to national security.
The halt is among the most substantial changes to U.S. surveillance policy in years and comes as issues of digital privacy remain contentious across the globe following the 2013 disclosures of broad NSA spying activity by former intelligence contractor Edward Snowden.
"NSA will no longer collect certain internet communications that merely mention a foreign intelligence target," the agency said in a statement. "Instead, NSA will limit such collection to internet communications that are sent directly to or from a foreign target."
NSA also said it would delete the "vast majority" of internet data collected under the surveillance program "to further protect the privacy of U.S. person communications."
The decision is an effort to remedy privacy compliance issues raised by rules implemented in 2011 by the Foreign Intelligence Surveillance Court, which operates in secrecy, sources familiar with the matter said.
The chief concern had been that the specific kind of collection sometimes produced surveillance of messages that were wholly domestic because of technical reasons.
The court recently approved the changes, NSA said in its statement.
The announcement, reported earlier Friday by The New York Times and Reuters, came as a surprise to privacy advocates who have long argued the activity, often called "about" collection, was overly broad and ran afoul of the U.S. Constitution's protections against unreasonable searches.
Julian Sanchez, a privacy and surveillance expert with the Cato Institute, a libertarian think tank, called the decision "very significant" and among the top priorities of surveillance reform among civil liberties groups.
"Usually you identify a specific individual to scrutinize their content; this was scrutinizing everyone's content to find mentions of an individual," Sanchez said.
Other privacy advocates seized on the change to advocate for additional reforms to the Foreign Intelligence Surveillance Act. The part of the law under which the ceased surveillance occurred, known as Section 702, is due to expire at the end of the year unless Congress reauthorizes them.
Democratic Senator Ron Wyden said in a statement he would introduce legislation "banning this kind of collection in the future."
NSA told the Privacy and Civil Liberties Oversight Board as recently as last year that changes to about collection were not "practical at this time," according to a report from the government watchdog.
News of the surveillance activity being halted was first reported Friday by The New York Times, which first revealed its existence in 2013 two months after Snowden leaked intelligence documents to journalists.
(Additional reporting by Mark Hosenball; Writing by Eric Beech; Editing by Tim Ahmann and Leslie Adler)