The need for functional security testing

Despite extensive testing of application functionality and security, we see many instances of software, when attacked or during normal operation, performing adversely in ways that were not anticipated. In large part, this is due to software assurance staff not testing fully for negative functionality, that is, ensuring that applications do not do what they are not supposed to. There are many reasons for this, including the relative enormity of the task, the pressure to implement quickly, and the lack of qualified testers. In this article, we will examine these issues and suggest ways in which we can achieve some measure of assurance that applications will not behave inappropriately under a broad range of conditions.