An efficient approach to tolerate attackers in fault-tolerant systems

Abstract: Malicious attackers can cause severe damage (financially or to the envi-ronment) if they gain control of safety-relevant systems. This paper shows why the traditional disjoint treatment of security and fault tolerance has weaknesses if the at-tacker gains access to the fault tolerant system and how an integrated approach that utilize existing fault tolerance techniques could be an effective security mechanism. An efficient integrated safety and security approach is presented for fault tolerant sys-tems, which achieves protection against attacks via the network by forming a logically isolated (sub-) network which is resilient against a bug in the codebase. Isolation is obtained by diverse design of a general reusable (software and/or hardware) compo-nent that prevents any unauthorized message transfer towards the secured application program. Messages from other compromised nodes are tolerated utilizing existing majority voting mechanism.