DiveInto: Supporting Diversity in Intrusion-Tolerant Systems

Intrusion tolerant services are usually implemented as replicated systems. If replicas execute identical software, then they share the same vulnerabilities and the whole system can be easily compromised if a single flaw is found. One solution to this problem is to introduce diversity by using different server implementations, but this increases the chances of incompatibility between replicas. This paper studies various kinds incompatibilities and presents a new methodology to evaluate the compliance of diverse server replicas. The methodology collects network traces to identify syntax and semantic violations, and to assist in their resolution. A tool called Dive Into was developed based on the methodology and was applied to three replication scenarios. The experiments demonstrate that Dive Into is capable of discovering various sorts of violations, including problems related with nondeterministic execution.