Who paid for that political ad in your Facebook feed? It's not always easy to figure out

Political advertisers are required to fill in a field that says who paid for the message in your news feed, but that does not necessarily tell you who they or their backers are. …A growing number of Facebook ads in the run-up to the election took advantage of that loophole to obscure or conceal the identity and political motives of who paid for them – and Facebook did not catch it. That allowed some Facebook pages to remain anonymous while stirring political discord. ..Facebook pages hawking ads that target Democrats or Republicans then bombard them with messaging from the other side of the aisle proliferated in the weeks before the midterm elections, according to Damon McCoy, an assistant professor of computer science and engineering at New York University’s Tandon School of Engineering. ‘Groups create these disingenuous, grassroots-looking communities on Facebook, and you can’t trace these damn things,’ he said. ‘There are so many of them, we can’t even catalog them all. They are popping up left and right.’