Dependability represents a critical requirement for modern distributed systems. Today new requirements emerged. Among them reliability, safety, availability, security and maintainability are needed by more and more modern distributed service computing architectures. In this paper we present an approach to ensuring dependability in distributed infrastructures using virtualization for fault-tolerance, augmented with advanced security models. The proposed solution is part of a hierarchical architectural model that allows a unitary and aggregate approach to dependability requirements while preserving scalability of large scale distributed systems. In this context we propose dependability solutions based on the use of virtualization and modern security models, combined together to automatically protect services and applications belonging to the distributed system. We also present evaluation results for several scenarios, involving applications and services with different characteristics.