Data provided to the Washington Post by former NSA contractor Edward Snowden show that during the 2009 to 2012 period, 160,000 e-mail and instant-message conversations intercepted by the NSA, as well as 7,900 documents taken from more than 11,000 online accounts. In the Post's analysis, half of the files contained details that the NSA had marked as belonging to US citizens or residents, which the agency masked, or "minimized," to protect those citizens' privacy.

"Nine of 10 account holders found in a large cache of intercepted conversations, which former NSA contractor Edward Snowden provided in full to The Post, were not the intended surveillance targets but were caught in a net the agency had cast for somebody else," the Post said.

The paper said the files also contained "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 U.S. computer networks."

But many more, belonging to more than 10,000 account holders, were unrealted to national security and are decidedly personal, detailing "love and heartbreak, illicit sexual liaisons, mental-health crises, political and religious conversions, financial anxieties and disappointed hopes," the Post said.

The e-mails and instant-messages were collected through the NSA's PRISM and Upstram programs, the Post said.