The emerging Multimedia Social Network (MSN) provides much more conveniences for the transmission and sharing of multimedia digital contents. However, the scenario on the distribution and spreading of copyrighted digital contents between users at will brings about a burning problem of Digital Rights Management (DRM). In addition, the open Internet and MSN platform are facing the security risks of digital contents copyrights infringements. The paper proposed a quantitative and qualitative-based risk analysis and assessment method, considering potential paths existence in MSN. Several risk impact factors was introduced, such as trust risk and user demands. Specifically, Value at Risk, a risk calculation method widely used in the financial field, as a quantitative analysis, was employed here. While an expert scoring sheet, as a qualitative approach, is used to evaluate non-quantifiable factors. Finally, the effectiveness of the security risk assessment method and related algorithm w...