Möbius 2.3 is an extensible dependability, security, and performance modeling environment for large-scale discrete-event systems. It provides multiple model formalisms and solution techniques, facilitating the representation of each part of a system in the formalism that is most appropriate for it, and the application of the solution method or methods best-suited to estimating the system's behavior. Since its initial release in 2001, many advances have been made in Möbius's design and implementation that have strengthened its place in the modeling and analysis community. With almost a decade of widespread academic and industrial use, Möbius has proven itself to be useful in a wide variety of modeling situations. This paper documents the current feature set of Möbius 2.3, emphasizing recent significant enhancements.