Speaking at a rally for Hillary Clinton at University of Michigan on Monday, Obama said: "The way campaigns have unfolded, we just start accepting crazy stuff as normal and people if they just repeat attacks enough and outright lies over and over again."
"As long as it's on Facebook, and people can see it, as long as its on social media, people start believing it, and it creates this dust cloud of nonsense," he told the gathering.
A follow-up probe by BuzzFeed revealed how teenagers in Macedonia create fake, pro-Trump news stories that go viral on Facebook.
Buzzfeed has also reported tweets encouraging people to vote by text which isn't possible.
Facebook has reiterated several times that it is working to improve the filtering of false and misleading stories from the News Feed.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)