In the context of the SysSec Network of Excellence call for consolidating the European (and international) systems security research community, this position paper aims at summarizing the current research activities in the Communication Systems Group (CSG) of ETH Zurich relating to network security. Our research is aligned along three projects: 1) identifying, validating, and characterizing computer infections from intrusion alerts, 2) building privacy-preserving collaborative network security mechanisms based on efficient secure multi-party computation (MPC) primitives, and 3) dissecting Internet background radiation towards live networks with one-way flow classification. In addition, we highlight important directions for future research.