Top intelligence officials indicated on Tuesday that the GOP was also a Russian hacking target but that none of the information obtained was leaked.
FBI director James Comey told a Senate panel that there was "penetration on the Republican side of the aisle and old Republican National Committee domains" no longer in use. Republicans have previously denied their organizations were hacked.
The testimony came in a Senate intelligence committee hearing that examined Russia's intrusions in the 2016 election campaign and its intentions, with America's top intelligence officials testifying just days after they released an unclassified report blaming Moscow for the hacks.
Comey later added that "there was evidence of hacking directed at state-level organizations, state-level campaigns, and the RNC, but old domains of the RNC, meaning old emails they weren't using. None of that was released."
Comey also said that the Russians "got far deeper and wider into the (Democratic National Committee) than the RNC," adding that "similar techniques were used in both cases."
Comey said the FBI would have preferred to "get access to the original device or server" that was the target of hacking at the DNC. CNN previously reported that the Democratic National Committee "rebuffed" a request from the FBI to examine its computer services after it was allegedly hacked by Russia during the 2016 election.
The FBI instead relied on the assessment of a third-party security company called CrowdStrIke. Comey told senators that the "highly respected private company eventually got access and shared" the evidence with the FBI.
Comey refused to comment on whether the FBI is investigating any potential connections between the Trump campaign and Russia "I would never comment on investigations," Comey told Sen. Ron Wyden, an Oregon Democrat who repeatedly pushed the FBI director to release any information it had.
The 17 US intelligence agencies already issued a statement in October expressing their unanimous assessment that Moscow had probed state election voting centers and penetrated the email accounts of Democratic groups and individuals. Much of that information was made public through the organization WikiLeaks, lead by Julian Assange.
In the final run-up to Nov. 9, Russia shifted its focus from influencing the campaign to undermining the validity of the results, a theme that Trump himself began to stress on the campaign trail, telling people the election was going to be "rigged."
Sen. Angus King of Maine, an Independent, alluded tartly to Comey's very public statements about investigations into Clinton during the election campaign -- "the irony of you making that statement I cannot avoid."
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