  In this paper we present an efficient approach to implementing model checking
in the Higher Order Logic (HOL) of Isabelle. This is a non-trivial task since
model checking is restricted to finite state sets. By restricting our scope to
considering security attacks, we achieve an efficient executable specification
of a model checking algorithm for attack trees. We provide the existing
background, the necessary theory and illustrate its application. Theory and
application are fully formalized in Isabelle thus providing an executable model
checking algorithm.
