  In times of Industry 4.0 and cyber-physical systems (CPS) providing security
is one of the biggest challenges. A cyber attack launched at a CPS poses a huge
threat, since a security incident may affect both the cyber and the physical
world. Since CPS are very flexible systems, which are capable of adapting to
environmental changes, it is important to keep an overview of the resulting
costs of providing security. However, research regarding CPS currently focuses
more on engineering secure systems and does not satisfactorily provide
approaches for evaluating the resulting costs. This paper presents an
interaction-based model for evaluating security costs in a CPS. Furthermore,
the paper demonstrates in a use case driven study, how this approach could be
used to model the resulting costs for guaranteeing security.
