Security is a critical issue in dynamic and open distributed environments such as network-based services or wireless networks. To ensure that a certain level of security is maintained in such environments, the system behavior has to be restrained by a security policy in order to regulate the nature and the context of actions that can be performed within the system, according to specific roles. In this paper, we propose a passive testing approach that permits to check whether a system respects its security policy. To reach this goal, we specify this policy using 'Nomad' formal language which is based on deontic and temporal logics. This language is well adapted to passive testing methods that aim to analyze collected system execution traces in order to give a verdict about their conformity with to the system security requirements. Finally, we apply our methodology to an industrial case study provided by SAP group to demonstrate its reliability