LONDON -- The U.S. Director of National Intelligence, Dan Coats, warned Friday of the intesifying threat of cyberattacks against the U.S., calling Russia "the most aggressive" offender. CBS News examines what's being done to crack down on foreign cyber invaders.

Ben Nimmo is a cyber investigator for the D.C.-based Atlantic Council. With the U.S. midterms approaching, he's teaching these activists and social media experts how to detect -- and expose -- Russian disinformation online.

"We know that elections are always a big juicy target," Nimmo said.

The aim is to head off the kind of Russian meddling that tainted the U.S. 2016 presidential campaign, but with the midterm primaries under way, Nimmo agrees with U.S. intelligence that Russian trolls and bots -- those are automated fake accounts -- are preparing a flood of toxic and divisive disinformation aimed squarely at U.S. voters.

Ben Nimmo CBS News

"You'll see lots of push on gun control, on immigration, race relations," Nimmo said. "All the old issues. Supreme Court, I would expect to see attacks."

CBS News agreed not to reveals where Ben Nimmo lives and works, because hunting down Russian hackers and trolls is dangerous business -- and he's received death threats. They even sent a fake obituary to all his contacts, tweeted the message that he's dead.

Social media giants like Facebook and Twitter are trying to shut down Russian fake accounts too, and so is U.S. intelligence, but they're simply overwhelmed.

Concrete proof: Nimmo has just exposed a huge Russian bot network lurking online, so well-disguised and pushing porn – it even fooled Twitter's new filter. All it would take is a single call from the Kremlin to sic it on the U.S. election.



Nimmo doesn't think the upcoming Trump-Putin summit could turn out so cordial that the that the Russian disinformation network will be called down - they won't interfere in the midterms.

"I think the probability of a Putin Trump meeting solving this disinformation problem is zero," Nimmo said.