Cloud computing opens new horizons for the development of computer and network; while users are likely to benefit from this technological revolution, they are also confronted with more security threats. The implementation of security framework in the cloud plays a pivotal role in convincing the customers that their service providers are trustworthy. Understandably, customers would be reluctant to adopt cloud services unless they are assured that the information is well protected. Information security is a critical but complicated issue. Despite all the proposed measures from the experts and researchers for reducing the risks, security incidents still occur. The inherent nature of cloud computing is furthermore accompanied by specific risks. Therefore in this paper we propose an all-encompassing perspective for examining and mitigating the security threats of cloud computing in various aspects, such as the organizational structure, the resource infrastructure, the system maintenance and operations. With the framework proposed in the paper, we hope to promote a best practice for providing security assurance within cloud computing.