The comments from Brennan come at a time of growing debate following last week's attacks in Paris about whether intelligence services have enough tools at their disposal to deal with tech-savvy jihadists as they plan attacks.
"Any unauthorised disclosures that are made by individuals who have dishonoured the oath of office that they raised their hand and attested to undermines this country's security," Brennan said at a Washington event in response to a question about Snowden.
"Hero-izing such individuals I find to be unfathomable as far as what it is that this country needs to be able to do again in order to keep itself safe."
The New York Times said in an opinion piece today that the comments by America's top spy were "disgraceful" and that the issue in last week's attacks in Paris was not a lack of data, "but a failure to act on information authorities already had."
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"Law enforcement agencies should have the necessary powers to detect and stop attacks before they happen," the Times said. "But that does not mean unquestioning acceptance of ineffective and very likely unconstitutional tactics that reduce civil liberties without making the public safer."
"Over the last five weeks or so, I have had a number of conversations with my Russian counterpart, despite the policy difference we may have in Syria and Ukraine," he said.
"These have been discussions about how we can in fact share more information about this threat from" the IS group.