Russian hackers were able to penetrate the control rooms of hundreds of U.S. utilities last year as part of a campaign against power company vendors that could be ongoing, The Wall Street Journal reported Monday.
Department of Homeland Security (DHS) officials told the Journal that hackers working for a state-sponsored group known as Dragonfly or Energetic Bear were able to get inside the networks of U.S. utilities to the point that they could have disrupted power service and caused blackouts, The Hill reported.
"They got to the point where they could have thrown switches," said Jonathan Homer, chief of industrial-control-system analysis for DHS.
The department did not disclose which companies were victimized by the hacks, but indicated there were hundreds affected by the breach. Other companies reportedly may still be unaware they were part of the breach because the hackers may have broken in using employee credentials.
The U.S. government had previously accused Russia of staging a multi-year cyberattack campaign against the energy grid and other elements of critical infrastructure in the United States.
It said the effort dated back to at least early 2016, and focused on networks belonging to small commercial facilities with the goal of working up toward larger energy companies.
The newly disclosed details of the Russian campaign comes amid growing concerns about Russia's efforts to interfere in the 2018 midterm elections.
President Trump has endured a week of criticism from Republicans and Democrats after he stood next Russian President Vladimir Putin in Finland and cast doubt on whether Russia interfered in the 2016 election.
He later walked back the statement and expressed confidence in the intelligence community's conclusion, though he added that it could have been others besides Russia that interfered.
Director of National Intelligence Dan Coats warned shortly before Trump met with Putin that "warning lights are blinking red" to indicate that Russia is preparing to launch another campaign to interfere in U.S. elections.