Snowden was claimed to have no access to the FISA data itself, and has not until now released any information on actual data. 9/10 instances of data handed over to the Washington Post was of innocent American citizens.

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 nevertheless.

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.

Among the latter are medical records sent from one family member to another, résumés from job hunters and academic transcripts of schoolchildren. In one photo, a young girl in religious dress beams at a camera outside a mosque.

There are many ways to be swept up incidentally in surveillance aimed at a valid foreign target. Some of those in the Snowden archive were monitored because they interacted directly with a target, but others had more-tenuous links.

If a target entered an online chat room, the NSA collected the words and identities of every person who posted there, regardless of subject, as well as every person who simply “lurked,” reading passively what other people wrote.

“1 target, 38 others on there,” one analyst wrote. She collected data on them all.

In other cases, the NSA designated as its target the Internet protocol, or IP, address of a computer server used by hundreds of people.