Architectural Approaches to Information Survivability

Abstract

Many large information systems have evolved to a point where the normal activities of society depend upon their continued operation. Significant concerns have been raised about the possible effects of failure in these systems. In this paper we discuss architectural approaches to improving the survivability of critical information systems and present a candidate architecture. The key features of the architecture are the use of a variety of shell structures (sometimes also known as wrappers) and the use of a network-wide approach to recovery and continued service. We discuss the design, implementation, and verification issues raised by the use of shells in complex distributed systems and introduce three types of shell: protection, enhancement, and correction. Combinations of these shells are used to ensure that the critical information system is protected against a wide variety of hazards ranging from software defects to malicious attacks. The implementation of shells is discussed and it is shown that the desirable characteristic of transparent implementation cannot generally be achieved, and that ensuring the correct operation of the shells is itself a significant issue. A demonstration system being developed for evaluation of the architectural concepts is presented.