therefore adopt the idea of aspect-oriented software development to tailor the formal part of a security engineering process towards security requirements of the system. Our method, termed aspect-oriented security engineering, is based on the idea of keeping each step in this process well-defined, small, and monotonic in terms of the degree of formalism. Our practical results focus on two use cases: first, model engineering for operating systems and middleware security policies; second, model analysis of runtime properties related to potential privilege escalation. We eventually combine both use cases to present a model- based reengineering approach for the access control system of Security- Enhanced Linux (SELinux).