WASHINGTON - Nine out of 10 people identified in a large cache of online conversations intercepted by the National Security Agency were ordinary Internet users and not foreign surveillance targets, a news report says.
Nearly half of the surveillance files were of United States citizens or residents, The Washington Post said of its four-month investigation of the trove of NSA-intercepted electronic data provided by fugitive NSA contractor Edward Snowden.
The revelations are likely to rekindle criticism in the US and abroad of US surveillance techniques and especially the NSA's vast data sweeps, and came after German authorities said they had arrested a suspected double-agent accused of spying for the United States.
"Ordinary Internet users, American and non-American alike, far outnumber legally targeted foreigners in the communications intercepted by the National Security Agency from US digital networks," the Post said.
The study was based on 160,000 emails and instant message conversations, as well as 7,900 documents taken from more than 11,000 online accounts, intercepted during President Barack Obama's first term in office (2009-2012).
The Post found that the NSA held on to material that analysts described as "useless."
These files "tell stories of love and heartbreak, illicit sexual liaisons, mental-health crises, political and religious conversions, financial anxieties and disappointed hopes."
Some of the files however did include "discoveries of considerable intelligence value."
That included "fresh revelations about a secret overseas nuclear project, double-dealing by an ostensible ally, a military calamity that befell an unfriendly power, and the identities of aggressive intruders into US computer networks."
The Post said: "The surveillance files highlight a policy dilemma that has been aired only abstractly in public.
"There are discoveries of considerable intelligence value in the intercepted messages -- and collateral harm to privacy on a scale that the Obama administration has not been willing to address."
Snowden, a 30-year-old former NSA contractor, was granted temporary asylum by Russia last August after shaking the US intelligence establishment with a series of devastating leaks on mass surveillance in the United States and around the world.
Last week the Post reported that all but four countries - Britain, Canada, Australia and New Zealand -- were seen as valid spy targets for the NSA.
Germany was outraged by revelations last year, again stemming from documents released by Snowden, that the NSA had allegedly eavesdropped on Chancellor Angela Merkel's conversations, as well as about wider US surveillance programs of Internet and phone communications.
The row strained ties between Washington and Germany, a key European ally, which both countries' leaders have been at pains to repair.
An independent privacy review board last week defended the NSA's vast foreign intelligence data sweep efforts, despite objections from civil liberties activists.
The Privacy and Civil Liberties Oversight Board, a panel created on the recommendation of the 9/11 Commission, formally adopted a report which called the NSA's overseas surveillance a valuable and legal tool in thwarting terrorism.
The panel said that the NSA's electronic snooping led to "well over 100 arrests" and helped smash numerous terrorist plots.