An extended misuse case notation Including vulnerabilities and the insider threat.pdf

An extended misuse case notation: Including vulnerabilities and the insider threat Lillian R?stad1 Norwegian University of Science and Technology, Trondheim, Norway Lillian.Rostad@idi.ntnu.no Abstract. Misuse cases are a useful technique for eliciting and mod- elling security requirements and threats. In addition they may be very useful in a risk analysis process, particularly as part of the system de- velopment process. The original misuse case notation adds inverted use cases to model threats and inverted actors to represent attackers. How- ever, an attack is usually performed by exploiting a vulnerability in a system and it would be useful to be able to represent vulnerable func- tions in a model. In addition, it should be possible to discern between insiders and outside attackers in a model, as they have very different abil- ities and potential for attacking a system. This paper therefore proposes an extended misuse case notation that includes the ability to represent vulnerabilities and the insider threat, and discusses the use of this ex- tended notation in the system development and risk analysis processes. 1 Introduction Security is being increasingly recognized as an important quality of IT-systems. Much of the reason for this can be explained by the evolution of IT-systems towards what Gary McGraw in [13] defines as the trinity of trouble: connectivity, extensibility and complexity. While these three properties typically improves the possibilities of what a system can do, they also significantly increases the risks. Being secure means having control and being able to keep the bad guys out - but the more complex a system is the harder it is to manage, and the possibility of third-party extensions only adds to the complexity. Connectivity is seductive as it greatly increases the potential use of a system, but it also greatly increases the number of attackers that can have a go at breaking into or otherwise harm the system. In some systems, like health care,