Platform as a service (PaaS) is a cloud computing service model that provides a computing platform and a solution stack as an on-demand service, allowing users to create, deploy and control their own cloud services without building and managing their own computing platforms. PaaS providers provide the networks, servers and storages alongside with the PaaS platform. Though cloud computing is getting prevalence in IT, security, in particular privacy, has incurred the most concerns from users. Using a cloud service, a user has no privilege in managing the underlying computing platform nor the underlying resource and infrastructure, leading to the situation that a user has no way to monitor cloud services' behavior to protect the user's privacy. This paper proposes a privacy enhancing framework on PaaS for detecting the privacy violating behavior and protecting user's information instantly by enforcing related protection actions. The proposed framework allows customized security policies and behavior analysis models, enabling users to impose application oriented privacy monitoring mechanisms.