Citing documents provided by former NSA contractor Edward Snowden, The Washington Post said that nearly half of those surveillance files contained names, email addresses or other details that the NSA marked as belonging to US citizens or residents.
The paper said the spy agency masked, or 'minimised', over 65,000 such references to protect Americans' privacy, but it found nearly 900 additional email addresses that could be strongly linked to US citizens or residents.
Without giving the details, it said that among the most valuable contents are "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."
"Months of tracking communications across more than 50 alias accounts, the files show, led directly to the 2011 capture in Abbottabad of Muhammad Tahir Shahzad, a Pakistan- based bomb builder, and Umar Patek, a suspect in a 2002 terrorist bombing on the Indonesian island of Bali," it said.
The paper said it was withholding other example at the request of CIA as it would compromise ongoing operations.
"Many other files, described as useless by the analysts but nonetheless retained, have a startlingly intimate, even voyeuristic quality. They tell stories of love and heartbreak, illicit sexual liaisons, mental-health crises, political and religious conversions, financial anxieties and disappointed hopes. The daily lives of more than 10,000 account holders who were not targeted are catalogued and recorded," it added.
The Post reviewed roughly 160,000 intercepted e-mail and instant-message conversations, some of them hundreds of pages long, and 7,900 documents taken from more than 11,000 online accounts.
The material spans President Barack Obama's first term, from 2009 to 2012, a period of exponential growth for the NSA's domestic collection.
"Taken together, the files offer an unprecedented vantage point on the changes wrought by Section 702 of the FISA (Foreign Intelligence Surveillance Act) amendments, which enabled the NSA to make freer use of methods that for 30 years had required probable cause and a warrant from a judge," the paper said.