Cyber Test Analysis and Simulation Environment (Cyber TASE) is a Centralized Test and Evaluation Investment Program (CTEIP) acquisition project designed to provide timely and accurate cyber evaluation assessments for military networks and systems. These include both C2 and Situation Awareness applications including systems such as the Global Command and Control System (GCCS). Cyber TASE has integrated and/or developed a set of innovative data collection, analysis, simulation, and visualization tools to provide a robust cyber assessment capability. Cyber TASE leverages live, virtual, and constructive (LVC) elements to assess and visualize cyber resilience of DoD systems; in addition, such analysis can be extended to assess resilience of specific missions, especially in cases when some parts of the system under test (SUT) are compromised by cyber attacks. CyberTASE includes a simulation component called Cyber TASE Constructive Simulator (CCS). The CCS is designed to mimic large scale, operationally relevant cyber scenarios for the target systems to be assessed. The CCS can operate in both faster than real-time and near real-time (NRT) execution modes to simulate cyber attacks on the target system. It also includes the capabilities to collect, report, and visualize relevant metrics from the simulated component. The CCS can be used to pre-run planned scenarios to predict outcomes and to perform “What - If� analysis over a larger parameter space encompassing network topologies, traffic profiles, cyber threats, and cyber defense architectures than would be possible using only live assets. In addition, the CCS directly supports LVC modeling of target systems via its support for real-time model execution, a set of interfaces to connect to live components, and virtual tap points to live data collectors. Thus, the CCS can be used to extend the target system to provide a scalable representation and to assess the cyber resilience of DoD systems in a wider system of systems context. Furthermore, the CCS can launch cyber attacks from the simulated network to expand the attack space for the target system, where cyber impact is limited to simulated devices within CCS. Finally, the CCS supports training use cases both for potential Cyber TASE users as well as for training red force role players. This paper describes the CCS architecture and illustrates its use via a specific example of cyber testing of a mission vignette for a representative set of cyber attacks intended to disrupt the mission.