Attack–defense trees are a novel methodology for graphical security modelling and assessment. They extend the well-known formalism of attack trees by allowing nodes that represent defensive measures to appear at any level of the tree.

Kordy, B., Mauw, S., Radomirović, S., & Schweitzer, P. (2014). Attack–defense trees. Journal of Logic and Computation, 24(1), 55-87. [Oxford Academic]