Misuse case

Misuse Case is a business process modeling tool used in the software development industry. The term Misuse Case or mis-use case is derived from and is the inverse of use case. The term was first used in the 1990s by Guttorm Sindre of the Norwegian University of Science and Technology, and Andreas L. Opdahl of the University of Bergen, Norway. It describes the process of executing a malicious act against a system, while use case can be used to describe any action taken by the system .

Use cases specify required behaviour of software and other products under development, and are essentially structured stories or scenarios detailing the normal behavior and usage of the software. A Misuse Case on the other hand highlights something that should not happen (i.e. a Negative Scenario) and the threats hence identified, help in defining new requirements, which are expressed as new Use Cases.

This modeling tool has several strengths:

Its biggest weakness is its simplicity. It needs to be combined with more powerful tools to establish an adequate plan for the execution of a project. One other weakness is its lack of structure and semantics.

In an industry it is important to describe a system's behavior when it responds to a request that originates from outside : the use cases have become popular for requirements between the engineers thanks to its features like the visual modeling technique, they describe a system from an actor's viewpoint and its format explicitly conveys each actor's goals and the flows the system must implement to accomplish them.

The level of abstraction of an use case model makes it an appropriate starting point for design activities, thanks to the use of UML use case diagrams and the end user's or domain expert's language. But for software security analyses, the developers should pay attention to negative scenarios and understand them. That is why, in the 1990s, the concept of "inverse of an use case" was born in Norway.

The contrast between the misuse case and the use case is the goal: the misuse case describes potential system behaviors that a system’s stakeholders consider unacceptable or, as Guttorm Sindre and Andreas L. Opdahl said, "a function that the system should not allow". This difference is also in the scenarios: a "positive" scenario is a sequence of actions leading to a Goal desired by a person or organization, while a "negative" one is a scenario whose goal is desired not to occur by the organization in question or desired by a hostile agent (not necessarily human).

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