Defining Digital Rights Management (DRM) is a complex task. There is no unique universal definition. There are many legal, economic, functional, and technical definitions. This complexity induces also that there is not one unique modeling of DRM. Each model should help to compare different DRM systems and easily highlight the differences and the similarities between them. One of the weaknesses of the current models is that none puts specifically the focus on the most important characteristics of DRM: protection of content and rights management. We propose a four-layer model that complements traditional ones. Using trust layer, rights management layer, rights enforcement layer, and content protection layer, this model is security oriented. It is suitable to describe any content protections such as DRM, conditional access, copy protection or even pre-recorded content protection systems.