One of the nation's top counterintelligence officials said Wednesday he knows "there are still a handful" of Russian intelligence officers operating undercover on U.S. soil, even after the Trump and Obama administrations kicked out nearly 100 such operatives over the past two years.Nevertheless, the director of the National Counterintelligence and Security Center, Bill Evanina, said the ousting of those known intelligence officers had a "decipherable, measurable" impact on the Russian government's ability to collect intelligence inside the United States.In March, after the poisoning of a former Russian spy and his daughter in the United Kingdom, the Trump administration expelled 60 Russian intelligence officers from the United States."I think there are still a handful left. I know there are," Evanina said. "And I think the White House is holding them out as potential sanctions in the future if activity continues."Speaking at the Aspen Institute in Washington on Wednesday, Evanina suggested that Russian aggression is unlikely to recede anytime soon, and he warned that Russian intelligence services are likely plotting future campaigns to interfere with the 2018 midterm elections and the presidential race in 2020 - a repeat of what they allegedly were able to accomplish in 2016."I think they exceeded their expectations of success," Evanina said of the election meddling. "They extremely succeeded."According to Evanina, Americans have yet to appreciate the extent to which Russian operatives are "utilizing our society against us."He pointed to how Russian operatives used social media platforms like Facebook to spread false information and inflame tensions across America."I don't think anybody really realized the capabilities that we saw," especially as outlined in a recent federal indictment charging 13 Russian nationals and three Russian companies for their roles a massive campaign to conduct what authorities described as "information warfare against the United States," with the stated goal of "spread[ing] distrust towards the candidates and the political system in general."One of the companies, the St. Petersburg-based Internet Research Agency, employed hundreds of people - from creators of fictitious personas to technical and administrative support - for its online operations, according to the Justice Department "After the election, the defendants allegedly staged rallies to support the President-elect while simultaneously staging rallies to protest his election," the Justice Department said in a press release. "For example, the defendants organized one rally to support the President-elect and another rally to oppose him-both in New York, on the same day."On Wednesday, Evanina said the U.S. government and public didn't recognize how far Russian officials were willing to go to "influence" the U.S. democratic process."The mindset to say, 'We're going to utilize a purely American part of our fabric - Facebook - to facilitate this discord,' is not only creative, but it's a mindset that we in the U.S. don't clearly take stock in," Evanina said.