An excerpt from the NBC report:

U.S. intelligence agencies are closely tracking attempts by foreign adversaries to influence the 2024 election through “deepfakes” or other false information and are ready to alert the public if necessary, officials said Wednesday.

A decision to notify the public about attempted election interference by foreign actors would be up to the leaders of the country’s intelligence agencies, including intelligence chief Avril Haines, officials from the Office of the Director of National Intelligence, or ODNI, told reporters.

The decision to issue a public warning would follow a review by digital forensic experts and intelligence analysts, the ODNI officials said. It would be based on an assessment of whether the disinformation was serious enough that it “could affect the election outcome,” an official said.

UPDATE: A slightly different take on the briefing here, from the AP.