This Project, the first one in network security field of the former members of what now is NESG, affords the design of a system for the detection of intruders, based on layers. In particular, the research team proposes the formal modeling of the network services considered, in order to make possible the detection of anomalies in the service provisioning. In addition, the project is also focused on the development of response mechanisms for the potential intrusions in the monitored scenario.