This article examines the presence of extremist online communities on the Russian social network VKontakte following the tightening by Russian federal аuthorities of internet counter-extremism policies and censorship. Extremist communities were detected using linguistic markers for extremist attitudes and radical violence. The study of socio-demographic data and network metrics of Islamist extremist communities reveals some general tendencies in the Russian context: a majority of female participants, a highly decentralised community network structure, radical Salafism as the mainstream ideology and covert proselytisation through the discussion of Islamic theology and lifestyle issues that are not in themselves extremist.