Many current approach to access control assume all external access are dangerous. As a consequence they stop all communication and check for authorisation. We present an optimistic approach to provide security services in a network environment that do not interject the security services into the operational sequence, rather, the security services are established as a parallel set of services/steps. This optimistic approach let go the communication and checks in parallel for authorization, illegal communication will be stopped latter. Provided that the checking is fast enough the potential danger may be kept as low as necessary. This presentation exhibits the concepts, properties, advantages of an optimistic access control. An implementation called “Network Security Probe”NSP* is described.