rently or soon to be available) in areas of threat modeling and critical infrastructure to provide near-term improvements in developing vulnerability assessments and risk mitigation strategies.

Currently, however, the U.S. government’s departments and agencies are in no position to make optimal use of available modeling and simulation technologies to support the creation of an overall strategy for their counterterrorism activities. They are not organized to assess terrorist threats, infrastructure vulnerabilities, and mitigation strategies from a systems perspective. Thus, although many initiatives have been proposed since September 11, and some—such as improving airport security, local emergency response, and seaport operations—are in early stages of implementation, they are often proceeding without the benefit of a systems approach. Specific examples of the value of systems approaches are also described in other chapters of this report, particularly Chapter 7, on transportation, and in Chapter 11, on crosscutting challenges.

While an overall systems approach is particularly important in the development of a national strategy for counterterrorism, there exist today models for particular infrastructures within the United States that have been produced by various government agencies and private industrial organizations. Aspects of energy distribution, power grids, air traffic control, and military support infrastructures have been analyzed and modeled to varying degrees of fidelity. In the near term, these models must be extended and expanded to provide better representation of specific critical infrastructures, and the models must be tested and evaluated against real-world data. A program to measure the interactions between various infrastructures must also be established. This effort will rely on determining the connectivity between infrastructures through analyses, model development, data collection, experiments, and model validation. At the same time a more detailed understanding of the implications of various threat scenarios for critical U.S. infrastructures must be established. The committee recognizes that it will never be possible to model the entire U.S. system in finite detail, but we can determine which components of our critical infrastructures are least robust; how an attack on one component of a particular infrastructure affects other systems; and which identified vulnerabilities within critical infrastructures are most vulnerable to a wide range of postulated threat scenarios.


When modeling terrorist networks and homeland systems, knowledge of the associated “architectural” framework—including its characteristic state variables1—is essential. In Figure 10.1, threats from terrorist networks constitute a


It should be noted that use of the term “state variable” is somewhat different from its use in, say, mathematics and control theory.

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