WASHINGTON (NEXSTAR) - U.S. officials are sounding the alarm over election misinformation online. They're warning of foreign actors trying to sow discord with fake videos and images.  "Just because it's on the internet doesn't mean it's true," Sen. Mark Warner (D-Va.) said.  Senate Intelligence Chairman Mark Warner says that advice is especially important now. He says foreign adversaries are expected to ramp up disinformation ahead of the election, often with fake videos or images on social media.  "If you had a deepfake of an election official destroying ballots, not only could that drive further dissension but it could literally lead to political violence," Warner said.  Warner says the threat is mostly from Russia, Iran and China. The Director of National Intelligence says those coutries "remain intent on fanning divisive narratives to divide Americans. "What they do is create lies, they put them online, they try to have an impact in the election," Sen. Marsha Blackburn (R-Tenn.) said.  Sen. Marsha Blackburn says she was recently a target of Chinese disinformation. She says social media platforms and users themselves have a role to play in recognizing those posts.  "What people need to do is build their awareness," Blackburn said. "Go to a reliable news outlet, they need to go to a reliable source," Blackburn said.  But how can you tell?  "It's almost a task that's too hard for us individually," George Washington University Professor in Complex Systems Neil Johnson said.  Johnson says it's getting harder by the day.  "It's no longer a case of looking for six fingers, or you know, three ears or something like that," Johnson said.  Johnson says it's going to take action from government, social media and journalists to address misinformation.  "It's the promotion of distrust and doubt. That's really what it comes down to," Johnson said.  And ultimately, the White House National Security Adviser Jake Sullivan says, "You should look at this as a national security issue, as an attack on our country."