Computer Networks: The International Journal of Computer and Telecommunications Networking
Proactive Fortification of Fault-Tolerant Services
OPODIS '09 Proceedings of the 13th International Conference on Principles of Distributed Systems
Towards a secure and available smart grid using intrusion tolerance
IDCS'12 Proceedings of the 5th international conference on Internet and Distributed Computing Systems
Computers and Electrical Engineering
The Journal of Supercomputing
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Nowadays, more and more information systems are connected to the Internet and offer Web interfaces to the general public or to a restricted set of users. Such openness makes them likely targets for intruders, and conventional protection techniques have been shown insufficient to prevent all intrusions in such open systems. This paper proposes a generic architecture to implement intrusion-tolerant Web servers. This architecture is based on redundancy and diversification principles, in order to increase the system resilience to attacks: usually, an attack targets a particular software, running on a particular platform, and fails on others. The architecture is composed of redundant proxies that mediate client requests to a redundant bank of diversified COTS\footnote{Commercial Off The Shelf.} application servers. The redundancy is deployed here to increase system availability and integrity. To improve performance, adaptive redundancy is applied: the redundancy level is selected according to the current alert level. The architecture can be used for static servers, i.e., for Web distribution of stable information (updated off-line), as well as for fully dynamic systems where information updates are executed immediately on an on-line database. The feasibility of this architecture has been demonstrated by implementing an example of a travel agency Web server.