Attack Trees with Sequential Conjunction
This work addresses a formalization gap for security analysts using attack trees, though it is incremental as it builds on existing attack tree frameworks.
The paper tackled the lack of a formal foundation for SAND attack trees, which extend attack trees with a sequential conjunctive operator to model ordered events, and provided a semantics, axiomatization, normal forms, and quantitative analysis methods.
We provide the first formal foundation of SAND attack trees which are a popular extension of the well-known attack trees. The SAND attack tree formalism increases the expressivity of attack trees by introducing the sequential conjunctive operator SAND. This operator enables the modeling of ordered events. We give a semantics to SAND attack trees by interpreting them as sets of series-parallel graphs and propose a complete axiomatization of this semantics. We define normal forms for SAND attack trees and a term rewriting system which allows identification of semantically equivalent trees. Finally, we formalize how to quantitatively analyze SAND attack trees using attributes.