The policy shift comes after a 2018 episode in Florida in which Democratic Sen. Bill Nelson said he had been told that Russian hackers gained access to some voting systems in his state, only to be accused of making that up by then-Gov. Rick Scott, the Republican running to unseat Nelson in that year's election. Scott said state officials had not been notified of any such breach.
Scott defeated Nelson. A few months later, special counsel Robert Mueller's report disclosed that Russian hackers did gain access to a voter registration network in a Florida county.
Sen. Marco Rubio, R-Fla., said in 2019 that intelligence officials, seeking to protect sources and methods, had issued only broad warnings to Florida's 67 election offices instead of informing the state of the specific breach. Gov. Ron DeSantis, elected in 2018, complained after taking office in 2019 that the FBI would not tell him which county's system had been breached.
FBI officials would not say whether this episode specifically prompted the policy change.
"We learned from a number of different experiences," the official said. "In looking at our experience over the past couple of years, we see that we can't treat every state the way we treat a large company."
Ken Dilanian is a correspondent covering intelligence and national security for the NBC News Investigative Unit.