On today's date 4 out of 5 people use the social networking sites for their social relationship buildings and be connected with their loved ones and friend circle. While building their social contact and relationships they shares lot more data and contents with each other. the social networking sites like Face Book, Google+ ,Twitter may provide the user's own space to share the contents like images , comments , other sharing contents and along with that the privacy policies also. But still there is a problem of privacy and security of data and content when the multiple users belong to the same content or data in any social networking sites. In this paper we propose the new system or an approach which protects the shared data in multiple user environments.Here we formulate the model for access control to overcome the problem of multiuser environment. And also we are providing the policy specification and enforcement mechanism. And also we will formulate the mechanism of authorization for shared data in OSNs. Here we will also focus on the fake identity in social networks and we will resolve that problem also. The scope of this proposed system is there where the privacy and protection of the shared data is important in multiuser environment like OSNs.The objective is to decrease the privacy issues in multiparty access control and to improve the protection and security of the shared data in OSNs when there are multiple parties to control. And to prevent the attack of fake identity on OSNs and provide the authorization mechanism in multiparty environment.