Although Donald Trump on Sunday again expressed doubt that Russia is behind hacks at the Democratic National Committee and other organizations, as well as the subsequent leak of emails and confidential documents to WikiLeaks, NBC News reported on Monday that Trump had received security briefings implicating the Russians prior to the debate.

“I notice, anytime anything wrong happens, they like to say the Russians are – she doesn't know if it's the Russians doing the hacking. Maybe there is no hacking,” Trump said of Clinton at the Oct. 9 presidential debate.

But NBC quoted a senior intelligence official as saying “both candidates have all the information they need to be crystal clear,” while noting that "to profess not to know at this point is willful misrepresentation."

Organizations affiliated with the Democratic Party have reported a number of breaches in recent months. The infiltrations are believed to be the work of two different Russian groups identified by CrowdStrike as Cozy Bear (aka CozyDuke or APT 29) and Fancy Bear (aka Sofacyor APT 28), working separately. The former is likely affiliated with Russia's military intelligence service, the GRU, according to CrowdStrike Co-founder and CTO Dimitri Alperovitch in a blog post. This group accessed the DNC network last summer where it monitored email and chat. 

But it wasn't until Fancy Bear, which Alperovitch said could be a surrogate of the Federal Security Service hacked into the network and pilfered two files in April that the DNC was alerted to the intrusion. The group was formerly led by Russian President Vladmir Putin, who has spoken favorably of Trump.

“We've had lots of experience with both of these actors attempting to target our customers in the past and know them well,” wrote Alperovich, who said CrowdStrike's incident response team was called in by the DNC. “In fact, our team considers them some of the best adversaries out of all the numerous nation-state, criminal and hacktivist/terrorist groups we encounter on a daily basis.”

But Trump has repeatedly questioned the veracity of claims that Russia is behind the hacks, most recently telling debate moderator Martha Raddatz that Clinton and the Democrats “always blame Russia. And the reason they blame Russia is because they think they're trying to tarnish me with Russia.”

The reality star/businessman turned presidential candidate has been under fire from critics for his praise of Putin and his alleged business dealings with Russian interests. Opponents have speculated that Trump hasn't yet released his tax returns because they might reveal such investments.

The candidate's latest pronouncements came just after the Department of Homeland Security and the Director of National Intelligence issued a joint statement saying they are "confident that the Russian government directed the recent compromises of emails from U.S. persons and institutions, including from U.S. political organizations.“

The disclosures of “alleged hacked emails on sites like and WikiLeaks and by the Guccifer 2.0 online persona are consistent with the methods and motivations of Russian-directed efforts. These thefts and disclosures are intended to interfere with the U.S. election process,” the statement said, adding that Russia has employed “similar tactics” in Europe and Eurasia. “We believe, based on the scope and sensitivity of these efforts, that only Russia's senior-most officials could have authorized these activities.”

Russia has repeatedly denied allegations that it is behind the hacks or that it seeks to influence the U.S. election. Additionally, WikiLeaks founder Julian Assange has refused to reveal the source of the emails that he has leaked thus far.