NSA whistleblower Edward Snowden took to Twitter on Monday to comment on the recent hack into Democratic National Committee inboxes, which resulted in 20,000 emails being published by WikiLeaks last week.

Snowden said Russia, which is widely suspected to be behind the hack, “should be condemned” if it is indeed responsible. He suggested that evidence of such an attack “certainly exists” at the National Security Agency, but has been kept under wraps out of fear of divulging too much information about its surveillance techniques and capabilities.

The hack exposed emails from top DNC staffers that appeared to undermine Bernie Sanders’ candidacy in favour of Hillary Clinton’s.

The leaks have raised fears of possible Russian interference in a US presidential election, or even collaboration with the Trump campaign — particularly since Trump and Russian President Vladimir Putin have publicly exchanged admiration for one another.

The Kremlin on Tuesday denied accusations that it hacked the DNC and called the allegations absurd, Reuters reported.

If Russia hacked the #DNC, they should be condemned for it. But during the #Sony hack, the FBI presented evidence. https://t.co/SG7er8VDRD

— Edward Snowden (@Snowden) July 25, 2016

Even if the attackers try to obfuscate origin, #XKEYSCORE makes following exfiltrated data easy. I did this personally against Chinese ops.

— Edward Snowden (@Snowden) July 25, 2016

Cybersecurity experts generally agree with Snowden’s assessment of the NSA — they say the agency likely does possess evidence of any Russian involvement involved, but there are numerous reasons for the government to keep that knowledge secret.

“It is actually very reasonable to conclude that the NSA does know the answer to this question without any real ambiguity,” Alex McGeorge, head of threat intelligence at Miami-based cybersecurity firm Immunity Inc., told Business Insider.

The NSA data analysis program XKeyscore, which was revealed by Snowden in 2013, is capable of intercepting communications at a variety of points and correlating sources and would probably be capable of determining the attacker, McGeorge said.

“It’s not easy, but that’s part of why they’re so good at their job,” he said.

Greg Martin, who founded the cybersecurity startup JASK and is a former advisor to the FBI, Secret Service, and NASA, agreed that the US intelligence community has substantial technical capabilities that it hasn’t shared with the public.

“More than likely, it is able to trace back the DNC breach to the true actor behind it,” he told Business Insider in an email.

But where the experts diverge with Snowden in opinion is with the government’s response to the hack — Snowden argued that since XKeyscore is now public, there’s little reason to keep evidence of a Russian cyber attack secret.

The aversion to sharing #NSA evidence is fear of revealing “sources and methods” of intel collection, but #XKEYSCORE is now publicly known.

— Edward Snowden (@Snowden) July 25, 2016

To summarize: the US Intel Community should modernise their position on disclosure. Defensive capabilities should be aggressively public.

— Edward Snowden (@Snowden) July 25, 2016

That would be a mistake, McGeorge said. The public knows that programs like XKeyscore exist and what types of data they collect, but not precisely how they work. The NSA likely wouldn’t be able to reveal evidence of Russian involvement without also disclosing the specifics of their surveillance capabilities.

“The NSA could say, ‘Yes we know the Russians did it.’ Would that be enough to satisfy the public? Or would they have to somehow say how they made that determination?” McGeorge said. “That is the key point that would give the Russians more than we perhaps want.”

But the significance of the breach may warrant a more forceful response than the government has displayed so far, Martin said. Interfering in a US presidential election was a bold move that “crossed the line” and could embolden the Russians in the future.

“At a minimum, the US government should have ‘named and shamed’ Russia and issued a strong diplomatic rebuke,” Martin said. “By not doing so, we’re setting a dangerous precedent for both us and our allies.”

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