Despite its many foreseen benefits, the main barrier to adoption of cloud computing remains security. Vulnerabilities introduced by virtualization of computing resources, and unclear effectiveness of traditional security architectures in fully virtualized networks raise many security challenges. The most critical issue remains resource sharing in a multi-tenant environment, which creates new attack vectors. The question is thus how to guarantee strong resource isolation, both on the computing and networking side. System and network complexity make manual security maintenance impossible by human administrators. Computing and networking isolation over virtualized environments should thus be achieved and automated. Unfortunately, current solutions fail to achieve that goal: hugely fragmented, they tackle the problem only from one side and at a given layer, thus without end-to-end guarantees. Moreover, they remain difficult to administer. A new integrated and more flexible approach is therefore needed. This paper describes a unified autonomic management framework for IaaS resource isolation, at different layers, and from both computing and networking perspectives. A nested architecture is proposed to orchestrate multiple autonomic security loops, both over views and layers, resulting in very flexible self-managed cloud resource isolation. A first design for the corresponding framework is also specified for a simple IaaS infrastructure