The main author of a string of stories revealing large-scale top secret spying on American citizens by the National Security Agency says that there are parts of the story that have been withheld for legal reasons and that the goal is not to execute an unedited document dump.

"We're not engaged in a mindless, indiscriminate document dump, and our source didn't want us to be," said Glenn Greenwald, the Guardian writer, in an email to BuzzFeed Saturday. "We're engaged in the standard journalistic assessment of whether the public value to publication outweighs any harms."

"I'm sure the Guardian has consulted lawyers about all of this, but as far as I know, none of the decisions have been legal, only journalstics," Greenwald said. He tweeted earlier on Saturday that the Guardian would not be publishing one of the full unredacted PowerPoint slides related to the PRISM datamining program, because "it contains very specific technical NSA means for collection - we'd probably be prosecuted if we did."

"We're applying the standard judgment test that journalists apply every day: first, is it newsworthy and relevant, ie, is there public interest in knowing this?" Greenwald told BuzzFeed. "If so: is there genuine harm that comes from publication? And if there is harm, does the public value outweigh/justify the harm?"

He said he didn't think there was "even a conceivable argument that anything we've published thus far causes any harm."

The series of leaks of highly classified information have prompted speculation as to the identity of Greenwald's source, as well as what could happen to this source if he or she (or they) is found out. Greenwald said on Saturday that his source knows the risks of whistleblowing in an era where leakers are aggressively sought out by the Department of Justice.

"Given that their central, motivating concern is that the NSA is constructing a global ubiquitous surveillance system to know what every person is doing and saying at all times, the source is of course aware of the exposure risks taken by any person who does anything, let alone one who discloses Top Secret information from one of the most secretive organizations in the world's most powerful government," Greenwald said.

"But people often take risks, and incur great self-sacrifice, in order to fight against pernicious threats and to achieve public good. That's what this source(s) is doing."

Asked if "source(s)" meant there were multiple people leaking the documents to the Guardian, Greenwald said "I'm just not comfortable right now saying if there's one or more than one, so I left it deliberately ambiguous."

On Saturday, Director of National Intelligence James Clapper released a statement accusing the press and whoever is leaking the NSA information of "reckless disclosures of intelligence community measures used to keep Americans safe."

"In a rush to publish, media outlets have not given the full context–including the extent to which these programs are overseen by all three branches of government–to these effective tools," Clapper said.

However, the public will largely have to take Clapper's word for it.

"Not all the inaccuracies can be corrected without further revealing classified information," he said in the statement. Clapper did declassify certain aspects of PRISM, including the parameters of how it collects data from tech companies.