Brazil was convulsed by massive digitally-enabled protests between June and August 2013. While largely peaceful, a militant anarchist group emerged during this period – the Black Bloc – which seized the public imagination. Although preoccupying media and policy makers, comparatively little is known about what Black Bloc is, where it comes from, or how it operates. This latest publication from the Open Empowerment Initiative considers the presence of Black Bloc in cyberspace. It focuses specifically on Facebook, the dominant social media platform used by more than 80% of Brazilian internet users.