https://www.reuters.com/article/us-facebook-ads/majority-of-divisive-facebook-ads-bought-by-suspicious-groups-study-idUSKBN1HN2KV

Most of the political ads about divisive issues that ran on Facebook Inc before the 2016 U.S. presidential election were sponsored by "suspicious groups" with no publicly available information about them, according to a study released on Monday and based on a database of five million ads on Facebook.