The article describes the research network “Analysis of extremist aspirations in social networks (X-SONAR)” funded by the Federal Ministry of Education and Research (BMBF). The network investigates extremist interaction and escalation dynamics in social online networks and their relevance for criminally relevant radicalization processes, such as in the planning and execution of extremist acts of violence. Among other things, the aim is to derive a model for risk assessment and prevention and to develop a demonstrator for a software-based tool that can be used by end-users from security agencies and civil society for on-demand monitoring of extremist agitation in virtual contexts.