Speaker: Robert Cole Title: Uncertain Numbers: An approach for representing epistemic uncertainty in Multi-Step Attack models Abstract: Probability theory is ideally suited to the representation of aleatory uncertainty while interval-based methods are more suited to the representation of epistemic uncertainty. In this presentation I will present a proposed approach for handling both types of uncertainty in the context of multi-step attacks. The concept of an uncertain number will be introduced and methods for arithmetic combination of uncertain numbers will be presented. Open research issues related to representing and propagating uncertainty will also be raised.