Model based security risk analysis is motivated by several factors:

• Improved precision in describing security relevant aspects will usually improve the quality of the analysis results.
• Using recent techniques for graphical modelling is expected to improve communication between the interested parties, and thereby reduce the risk of misunderstandings.
• Using formal methods improve the possibility for re-use, which should reduce maintenance costs.
• Close integration of security analysis in the system development process is expected to reduce development costs as well as making it easier to reach an acceptable security level.
• Model based security risk analysis supports model driven system development.

Our method, CORAS, is based on the idea that requirement analysis and risk analysis are two closely related activities. During a requirement analysis the focus is mainly on documenting the required functionality of a system. In risk analysis you also want to understand how the system works, but the focus is on threat scenarios and unwanted behaviour.

More information on CORAS is available at http://coras.sourceforge.net/.