Virtual Interacting Network CommunIty (Vinci) is a software architecture that exploits virtualization to secure a community cloud, i.e. a cloud system shared among communities with distinct security levels and reliability requirements. A community consists of a set of users, their applications, a set of services and of shared resources. Users with distinct privileges and applications with distinct trust levels belong to distinct communities. Rather than acquiring and managing its own physical infrastructure, a community defines a virtual ICT infrastructure, i.e. an overlay, by instantiating and interconnecting Virtual Machines (VMs) defined from a small set of templates.