This document constitutes the first deliverable of MAFTIA work package 1. The objective of this work package is to define a consistent framework for ensuring the dependability of distributed applications in the face of a wide class of threats. In particular, the aim is to develop a coherent set of concepts for an architecture that can tolerate deliberately malicious faults, such as intrusions, in applications distributed over the Internet. The intrusions of concern include not only those perpetrated by external penetrators, but also those carried out by corrupt insiders, i.e., users who are authorized to access the system but not authorized for the accessed data, program or resource, and administrators who misuse their rights. Although intr...