Testing for software vulnerability using environment perturbation

Describes a methodology for testing a software system for possible security flaws. Based on the observation that most security flaws are caused by a program´s inappropriate interactions with the environment and are triggered by a user´s malicious perturbation on the environment (which we call an “environment fault”), we view the security testing problem as the problem of testing for the fault-tolerance properties of a software system. We consider each environment perturbation as a fault, and the resulting security compromise as a failure in the toleration of such faults. Our approach is based on the well-known technique of fault injection. Environment faults are injected into the system under test, and the system´s behavior is observed. A failure to tolerate faults is an indicator of a potential security flaw in the system. An environment-application interaction (EAI) fault model is proposed which guides us to decide what faults to inject. Based on EAI, we have developed a security testing methodology, and we have applied it to several applications. We have successfully identified a number of vulnerabilities, including vulnerabilities in the Windows NT operating system