News organisations publishing leaked National Security Agency documents have inadvertently disclosed the names of at least six intelligence workers and other government secrets they never intended to give away, an Associated Press review has found.
The accidental disclosures illustrate the risks of even wellintentioned, public-interest reporting on highly secret US programmes.
In some cases, prominent newspapers including The New York Times quickly pulled down government records they published online and recensored them to hide information they accidentally exposed.
On one occasion, The Guardian newspaper published an NSA document that appeared to identify an American intelligence target living abroad. Before the newspaper could fix its mistake, a curious software engineer, Ron Garret of Emerald Hills in the US state of California, tried to contact the man at his office.
"I figured someone ought to give him the heads up," Garret said.
The inadvertent disclosures, which include technical details and other information, are another complication in the ethically and technically challenging coverage of the NSA's surveillance programmes. Journalists who have seen the unfiltered secrets leaked by former intelligence worker Edward Snowden agree that some things are off-limits for publication. But media organisations sometimes have struggled to keep them that way.
Glenn Greenwald, the reporter and columnist who has played a key role in publishing so many of Snowden's revelations, has said he wouldn't publish the names of US intelligence workers unless they were top-ranking public officials. Greenwald said that the mistaken disclosures of at least six names and other material were minor errors made by technical staff and quickly corrected.
It was not immediately clear what damage, if any, has come from the disclosures of the names of the six NSA employees and other secrets. The NSA would not discuss its employees. None appeared to be working undercover.
The Associated Press was able to locate several of their home addresses and other personal details about them.
The accidental disclosures involve carelessness by some television broadcasters, sloppy digital redactions applied to copies of documents and, in The Guardian's case, an incomplete understanding of what information might be revealing.
The Canadian Broadcasting Corporation's nightly news programme, The National, revealed the names of three NSA employees when its cameras panned across NSA documents during voice-overs.
CBC's director of news content, David Walmsley, said the network regretted the error, pulled the video off its website and purged the material from its servers.
"It was a mistake that occurred because we had pixilated the documents and we thought we'd done it well enough. Clearly we didn't," he said.
Walmsley said the CBC took responsibility for the mistake. He said Greenwald had asked that NSA employee names not be broadcast.
The same thing happened at the Brazilian television station Globo, which briefly exposed the names of two NSA employees during its weekly news programme Fantastico last year.
The New York Times published an NSA presentation last month with the name of an NSA employee marked out. But a quirk of electronic documents is that information can linger even when it's invisible to the naked eye. Within minutes of the newspaper's report, the employee's name was circulating.
A spokeswoman for the newspaper blamed a production error and said the document was removed, recensored and republished.