FBI director Christopher Wray testified on Thursday that Russia was actively attempting to influence the 2020 election by trying to denigrate Joe Biden through "malign foreign influence".
Meanwhile, a "steady drumbeat of misinformation" to create the perception, though not the reality, of insecure elections was the biggest concern for election security, Mr Wray told the House homeland security committee on Capitol Hill.
He said the agency had seen "very active" efforts by the Russians through social media, state media, online journals and use of proxies in an effort to sow divisiveness and discord against what it sees as the "anti-Russian establishment" of the Democratic candidate. That is counter to Moscow's efforts in 2016 that focused on efforts to hack emails and election systems.
Mr Wray said the FBI has recently alerted Facebook and Twitter to fake accounts traced back to Russia, which were subsequently removed.
The testimony comes after a warning on 7 August by National Counterintelligence and Security Centre that Russia, China, and Iran were attempting to interfere in US politics, although the Trump administration has tried to play down the role of Moscow.
While Mr Wray didn't offer any further specifics about the interference efforts, he said his biggest concern was the perception of election insecurity that would leave people feeling their votes are futile.
"In many ways what concerns me the most is the steady drumbeat of misinformation, and sort of amplification of smaller cyber intrusions that contribute over time, I worry that they will contribute over time to a lack of confidence of American voters and citizens in the validity of their vote," he said.
"I think that would be a perception, not a reality. I think Americans can and should have confidence in our election system and certainly in our democracy, but I worry that people will take on a feeling of futility because of all of the noise and confusion that's generated."
When it came to China, Mr Wray said the FBI was opening a new counterintelligence investigation related to China every 10 hours to monitor its efforts to steal US technology and other information.
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