fault tree

A branching, hierarchical data structure that is used to represent events and to determine the various combinations of component failures and human acts that could result in a specified undesirable system event. (See: attack tree, flaw hypothesis methodology.)

Tutorial: "Fault-tree analysis" is a technique in which an undesired state of a system is specified and the system is studied in the context of its environment and operation to find all credible ways in which the event could occur. The specified fault event is represented as the root of the tree. The remainder of the tree represents AND or OR combinations of subevents, and sequential combinations of subevents, that could cause the root event to occur. The main purpose of a fault-tree analysis is to calculate the probability of the root event, using statistics or other analytical methods and incorporating actual or predicted

quantitative reliability and maintainability data. When the root event is a security violation, and some of the subevents are deliberate acts intended to achieve the root event, then the fault tree is an attack tree.