The latest revelations about Russian Federation and Iran obtaining American voters' registration records throws a bombshell twist into the presidential campaign less than two weeks before the election.
The messages warned "we will come after you" if the recipients did not vote for Donald Trump.
Ratcliffe revealed Iran has so far used the voter information to send "spoof emails created to intimidate voters, incite social unrest and damage President Trump".
The U.S. Federal Bureau of Investigation and intelligence community officials say Iran and Russian Federation have "taken specific actions to influence public opinion" in the upcoming presidential election. So officials say they focus on the adjacent systems and, more broadly, on trying to change people's minds - including with deliberate attempts at spreading misleading or false stories to shape the US information environment.
Some of those emails also contained a video, debunked by experts, that purported to show how fake ballots could be submitted.
Ratcliffe said the spoofed emails were meant to hurt Trump, though he did not elaborate on how.
"We have confirmed that some voter registration information has been obtained by Iran, and separately, by Russia", Mr Ratcliffe said during a hastily-arranged news conference.
"Ahead of the 2020 US elections, foreign states will continue to use covert and overt influence measures in their attempts to sway USA voters' preferences and perspectives, shift USA policies, increase discord in the United States, and undermine the American people's confidence in our democratic process", William Evanina, director of the United States National Counterintelligence and Security Center, said.
"We have not seen any adversary, anyone with that sort of capability - to be able to change a vote in the outcome of the election at the national scale is incredibly hard to accomplish", Krebs explained. "Iran's efforts along these lines probably will focus on online influence, such as spreading disinformation on social media and recirculating anti-U.S. content".
The news comes a day before Trump and his Democratic challenger Joe Biden are scheduled to take part in the final presidential debate.
But such tactics were going on well before 2020.
The FBI has issued an urgent warning about interference in the U.S. election, after the agency discovered voter information has been obtained by foreign sources. "However, this incident marks a fundamental shift in our understanding of Iran's willingness to interfere in the democratic process", said John Hultquist, senior director of analysis for Mandiant Threat Intelligence. Russia's Internet Research Agency set up thousands of social media accounts created to smear Hillary Clinton, the Democratic candidate.
He urged "every American" to make sure the interference efforts do not achieve their goal.
That warning was repeated during Wednesday night's briefing, with Federal Bureau of Investigation director Mr Wray urging voters: "Be thoughtful, careful and discerning consumers of information online".