: This paper proposes a context-aware security service providing multiple authentications and authorization from a Security Level which is decided dynamically in a context-aware environment. It helps developers build secure services efficiently. A security service in a dynamic environment uses Multi-Attribute Utility Theory and extended Generalized Role-Based Access Control. The system uses attribute values in GRBAC to calculate the Security Level, and extend the GRBAC. We expect this model to be widely used in providing flexible security services in a heterogeneous network.