Despite the increased focus on security, critical information systems remain vulnerable to cyber attacks. The trend lends importance to the concept of intrusion tolerance: there is a high probability that systems will be successfully attacked and a critical system must fend off or at least limit the damage caused by unknown and/or undetected attacks. In prior work, we developed a Self-Cleansing Intrusion Tolerance (SCIT) architecture that achieves the above goal by constantly cleansing the servers and rotating the role of individual servers. In this paper1 , we show that SCIT operations can be incorruptibly enforced with hardware enhancements. We then present an incorruptible SCIT design for use by one of the most critical infrastructures of the Internet, the domain name systems. We will show the advantages of our designs in the following areas: (1) incorruptible intrusion tolerance, (2) high availability, (3) scalability, the support for using high degrees of hardware/server redundanc...