Misuse case. Determine dangers faced by the system.
What is a misuse case? What advantages do they offer and how are misuse cases created?
Misuse cases are “upside down” use cases with which to collect features that the system should not allow. This way, you can find security measures that increase the quality of the system.
A misuse case can attack a use case. On the other hand, a use case is in the position to weaken or prevent misuse cases. That is why there are two new types of relationships in the use case diagram.
A misuse case is always linked with a misactor: A person who, deliberately or accidentally, causes damage to the system.
What does the software have to be able to do? Which features should it provide? These are typical questions that requirements engineering attempts to clarify. For this, use cases are created and normally the use case diagram is used to visualize it. But what about about stakeholders’ goals and desires that don’t fit into that? “The system must be completely secure!” is an example of something your customers might say. Good, you think, and create a security requirement that should increase the quality of the system. But this is rather broadly described and difficult to examine. Could a use case be formed from this? Unfortunately, the answer to this is: no, use cases are only recommended for functional requirements – so, descriptions of implementable features. To be able to derive quality requirements (non-functional requirements), you have to think the other way around – what should the system NOT be able to do? Or in this case: what should the system hinder so that it is secure? And then misuse cases come into play.
What is a misuse case?
Misuse cases were described for the first time in 2001 by Guttorm Sindre and Andreas Opdahl, two Norwegian professors in the area of information system development, for requirements in the area of system security. They explained the known requirements process with use cases and use cases diagrams. A misuse case can be imagined as an inside-out use case – so, a feature that should not be implementable in a system. It offers another viewpoint of the system to manage security requirements. Above all, these requirements are very meaningful according to the Kano model of stakeholder satisfaction.
Advantages of misuse cases
- Quality is increased because non-functional requirements are noticed
- Developers and customers can better understand the system
- Model is easy to understand and use
- Measures are immediately visible because risks and counter-measures are visualized
- Risk analysis is possible early on
- Risks can be recognized customer-specifically
- Traceability is ensured because features to increase security have to be revised
