Survivability through customization and adaptability: the Cactus approach

Survivability, the ability of a system to tolerate intentional attacks or accidental failures or errors, is becoming increasingly important with the extended use of computer systems in society. While techniques such as cryptographic methods, intrusion detection, and traditional fault tolerance are currently being used to improve the survivability of such systems, new approaches are needed to help reach the levels that will be required in the near future. This paper proposes the use of fine-grain customization and dynamic adaptation as key enabling technologies in a new approach designed to achieve this goal. Customization not only supports software diversity, but also allows customized tradeoffs to be made between different QoS attributes including performance, security, reliability and survivability. Dynamic adaptation allows survivable services to change their behavior at runtime as a reaction to anticipated or detected intrusions or failures. The Cactus system provides support for both fine-grain customization and dynamic adaptation, thereby offering a potential solution for building survivable software in networked systems.