An approach to measure the operational security of intrusion tolerant systems

A new approach to evaluate the operational security of the Intrusion Tolerant System (ITS) is proposed. It is based on the mapping of the concept of the system security into that of system dependability. This approach permits to consider in the unified viewall the security strategies and mechanisms to realize the defense system. Therefore the semi-Markov process is used to emulate the variability of the fault rate. Owing to the strong connection of the operational security of ITS with the attributes of system dependability (availability, integrity, confidentiality and reliability), the measurement procedure is pointed out to estimate the security parameters (availability, integrity, confidentiality), and the index for the operational security evaluation. This last is the Mean Time To Security Failure and is correlated to the attribute of system reliability. Indeed, it takes into consideration as long is immunity of the system to the attack. Numerical results of three case studies are shown to validate the measurement procedure.