President Obama warned Russia on Friday not to wage cyberwarfare against the United States, saying, “We can do stuff to you” as he defended his handling of Moscow’s alleged hacking of Democrats’ emails to influence the 2016 election.

“Our goal continues to be to send a clear message to Russia or others not to do this to us, because we can do stuff to you,” Obama told reporters at his final press conference of 2016.

His comments came shortly after it was disclosed that the FBI agrees with the CIA’s conclusions that Russia targeted Democrats with the aim of helping President-elect Donald Trump win on Nov. 8.

Obama promised that any U.S. retaliation against Russia would come “in a thoughtful, methodical way” that might be hidden from the U.S. public.

“Some of it we do publicly, some of it we will do in a way that they know but not everybody will,” he said. “The message will be directly received by the Russians and not publicized.”

Obama defended his response to Moscow’s alleged intrusion, saying, “We handled it the way it should have been handled.”