The joint project 'X-SONAR: Extremist Engagement in Social Media Networks: Identifying, Analyzing and Preventing Processes of Radicalization' conducts applied and fundamental interdisciplinary research on the dynamics and escalation of extremist interactions in social online networks. More specifically, X-SONAR analyzes mechanisms of individual and collective dynamics of violence as well as self-regulation of radicalism within these networks. Online radicalization and the escalation of violence on the internet are relevant not only in regard to prosecution, but also require new pathways for early warning and the development of appropriate prevention measures.