This paper proposes a new model, based on mainstream game theory for the optimal configuration of services. We consider the case of reliable realtime P2P communications and show how the configuration of security mechanisms can be configured using game theoretical concepts, in which the defendant is played by the management plane having to face adversaries which play the attacker role. Our main contribution lies in proposing a risk assessment framework and deriving optimal strategies - in terms of Nash equilibrium - for both the attacker and the defendant. We consider the specific service of communications in autonomic networks and we show how the optimal configuration can be determined within the proposed framework.