Despite the increased focus on security, critical information systems remain vulnerable to cyber attacks. The problem stems in large part from the constant innovation and evolution of attack techniques. The trend lends importance to the concept of intrusion tolerance: 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 paper, we show that, with simple hardware enhancements strategically placed in a SCIT system, incorruptible intrusion containment can be realized. We then present an incorruptible SCIT design for use by one of the most critical infrastructures of the Internet, the domain name services. It is our belief that incorruptible intrusion containment as presented here constitutes a new, effective layer of system defense fo...