Facebook estimates the 3,000 ads bought by the Kremlin-linked Internet Research Agency between 2015 and 2017 reached as many as 10 million users in the United States. And according to Facebook, more than half of those ads (56%) showed up after the 2016 election, indicating Russian interference may be an ongoing issue.
In response to news reports that Russians also used a Facebook-provided targeting tool called Custom Audiences, Facebook says that is true of only about 1% of the ads. Elliot Schrage, Facebook's Vice President of Policy and Communications, explains that targeting has useful applications, allowing advertisers to reach interested parties and exclude those who are not likely to purchase specific goods and services. But in the wake of Russian operatives using the tool to spread controversial and divisive content, Schrage says that going forward, "ads containing certain types of targeting will now require additional human review and approval."
Schrage's full post: Hard Questions: Russian Ads Delivered to Congress (Facebook newsroom)