When designing secure information systems, a profound understanding of the threats that they are exposed to is indispensable. Today's most severe risks come from malicious threat agents exploiting a variety of attack vectors to achieve their goals, rather than from random opportunistic threats such as malware. Most security analyses, however, focus on fixing technical weaknesses, but do not account for sophisticated combinations of attack mechanisms and heterogeneity in adversaries' motivations, resources, capabilities, or points of access. In order to address these shortcomings and, thus, to provide security analysts with a tool that makes it possible to also identify emergent weaknesses that may arise from dynamic interactions of attacks, we have combined rich conceptual modeling of security knowledge with attack graph generation and discrete-event simulation techniques. This paper describes the prototypical implementation of the resulting security analysis tool and demonstrates how it can be used for an experimental evaluation of a system's resilience against various adversaries.