https://www.vox.com/policy-and-politics/2018/4/18/17247010/what-is-going-on-with-facebook-russia-ads

According to a new study, “suspicious” groups were behind half of divisive political ads on Facebook in the 2016 election, and one-sixth of those were linked to Russia.

Evidence continues to trickle out about how Russians and potentially other bad actors used Facebook to spread disinformation during the 2016 campaign. The latest piece of information: a new study that found that more than half of the sponsors of Facebook ads that featured divisive political messages ahead of the 2016 election were from “suspicious” groups with little or no paper trails to identify them.