In 2018, researchers from the Data & Society think tank identified the YouTube recommendation system as promoting a range of political positions from mainstream libertarianism and conservatism to overt white nationalism. Many other online discussion groups and forums are used for online right-wing radicalization. Facebook was found to be offering advertisements targeted to 168,000 users in a white genocide conspiracy theory category, which they removed shortly after being contacted by journalists in the wake of the 2018 Pittsburgh synagogue shooting. After the March 15, 2019 Christchurch mosque shootings, Facebook announced that they have banned white nationalist and white separatist content along with white supremacy.