ONE SECOND AFTER: Russian hackers infiltrated US power networks and had the ability to trigger massive blackouts.

Symantec first reported on a hacking campaign by the state-sponsored group Dragonfly targeting dozens of victims in the US energy sector in 2017. But this is the first time the DHS has provided detailed information about an incident in an unclassified setting and said the hack affected “hundreds of victims.”

Attacks began in 2016 and continued through 2017, and DHS officials said it’s likely the campaign is still ongoing.

By first penetrating the networks of power companies’ trusted vendors, hackers for Dragonfly, also known as Energetic Bear, were able to access utility networks, The Wall Street Journal reported Monday, citing officials at the DHS.

As was proven with Stuxnet a few years ago, even air-gapped computer systems aren’t immune to hacking.