WaPo:

The U.S. military discovered that an Iranian hacking group had penetrated a local government website that was to report 2020 election results and disrupted the attack before the votes were tallied, officials revealed Monday during a conference of cybersecurity professionals.

Officials said that while neither the votes nor the counting machines would have been affected by the intrusion, the hackers could have rendered the public-facing website for displaying results unreachable or posted fake results, shaking public confidence in the true results.

“It could make it look like the votes had been tampered with,” said Maj. Gen. William J. Hartman, commander of the Cyber Command’s Cyber National Mission Force.

Hartman did not reveal which website had been penetrated. He said his group of 2,000 cyber experts discovered the penetration during its “hunt forward” efforts overseas, then alerted the Department of Homeland Security, which helped the unnamed local government thwart the intrusion.

Hartman spoke during a rare joint presentation with the head of the DHS agency for domestic cyberdefense at the annual RSA security industry conference in San Francisco. Until his presentation Monday, the Iranian intrusion had been classified.