Intrusion tolerant system for servers

Systems that provide continuous critical missions demand the capability of withstanding attacks and intrusions. Services (possibly degraded) are provided continued even though systems are been attacking or have been faults. This paper simply discusses principles of intrusion tolerance firstly. Then it presents strategies of intrusion tolerance aiming at servers under monitoring resources and behaves of servers' system. And resource reallocation algorithm is also described particularly. The algorithm provides enough resources for the critical services by sacrificing non-critical services. Some methods such as auditing and validating and resources bereaved are adopted to recover or degrade systems while they are been attacking. Finally, we have developed an intrusion tolerant system for web server. Experiment results show that the system is very effective to cope with not only denial of service attacks but also integrity attacks.