Organizations should use from enterprise security architectures to secure their information assets. ‎Security patterns are a good way to build and test new security mechanisms. Enterprise security pattern ‎as an instance of model-driven architecture offers a solution to recurring information systems security ‎problems. In this paper, we present a model-driven enterprise security pattern called Secure SaaS., which ‎the organizations could apply to protect their information assets when using SaaS. On the other hand ‎Cloud Computing is a approach for the efficient use of computational resources. cloud delivers ‎computing as a service. However, security concerns prevent many individuals and organizations from ‎using clouds. Second section of this paper focuses on the Security problem of Platform-as-a-Service ‎‎(PaaS) clouds including access control, privacy and service continuity while protecting both the service ‎provider and the user. Security problems of PaaS clouds are explored and classified. Countermeasures ‎are proposed and discussed. ‎