Building a Reactive Immune System for Software Services

We propose a new approach for reacting to a wide variety of software failures, ranging from remotely exploitable vulnerabilities to more mundane bugs that cause abnormal program termination (e.g., illegal memory dereference). Our emphasis is in creating 'self-healing' software that can protect itself against a recurring fault until a more comprehensive fix is applied. Our system consists of a set of sensors that monitor applications for various types of failure and an instruction-level emulator that is invoked for selected parts of a program's code. Use of such an emulator allows us to predict recurrences of faults, and recover program execution to a safe control flow. Using the emulator for small pieces of code, as directed by the sensors, allows us to minimize the performance impact on the immunized application. We discuss the overall system architecture and a prototype implementation for the x86 platform. We evaluate the efficacy of our approach against a range of attacks and other software failures and investigate its performance impact on several server-type applications. We conclude that our system is effective in preventing the recurrence of a wide variety of software failures at a small performance cost.