The breadth and variety of these statistics are reflected in the Department of Homeland Security's (DHS's) complex border security mission, which calls on the agency to "prevent the illegal flow of people and goods across U.S. air, land, and sea borders while expediting the safe flow of lawful travel and commerce; ensure security and resilience of global movement systems; [and] disrupt and dismantle transnational organizations that engage in smuggling and trafficking across the U.S. This report focuses on the first major step in managing border-related risks: assessing the risk posed by different types of threats at U.S. borders. This report begins with a discussion of the types of threats the United States confronts at its international borders (see " Types of Border Threats "), followed by an overview of DHS's risk management methodologies, including in the context of border security (see " DHS and Risk Management "). The report concludes by placing threat assessment within the broader context of border security policymaking. Threat Actors

Any person who intends to harm the United States, or whose presence may lead to harmful consequences, may be considered a threat and a potential target for border enforcement policies. The key differences among terrorists, transnational criminals, and unauthorized migrants are summarized in Figure 2 ; the threats associated with these different types of border flows are discussed below (see " Evaluating Potential Consequences of Border Threats "). Illegal goods fall into two broad categories distinguished by their inherent illegitimacy : certain weapons, illegal drugs, and counterfeit goods are always illegal and categorically prohibited, while other goods are generally legal, but become illegitimate because they are smuggled to avoid the enforcement of specific laws, taxes, or regulations. DHS, for instance, has identified "high-consequence weapons of mass destruction (WMD)" as one of the primary threats to homeland security. A Framework for Assessing Border Threats

The diversity of border threats and the complexity of DHS's border security and border management mission create challenges for border security policymaking and planning. Rather than attempting specific predictions about where, when, and how border threats will be realized, DHS and other analysts often rely on risk management as an approach to border security, and on probabilistic risk models as a framework for analyzing and describing different types of potential threats. Understanding border threats can be a logical starting point for this process. The Strategic Actor Problem

Beyond these definitional and measurement problems, an additional obstacle to estimating the likelihood of particular border threats is that threat actors like unauthorized migrants, transnational criminal organizations, and potential terrorists are strategic and may adapt their behavior in response to U.S. border enforcement efforts. Members of Congress may reach different conclusions about potential consequences at each stage of this evaluation process. This report describes a possible framework for describing the risks posed by specific hazards at the border based on their likelihood and their potential consequences. As budgeting has grown tighter in the current fiscal climate, policymakers face increasingly difficult questions about how to set priorities and where to allocate scarce resources.
The United States confronts a wide array of threats at U.S. borders, ranging from terrorists who may have weapons of mass destruction, to transnational criminals smuggling drugs or counterfeit goods, to unauthorized migrants intending to live and work in the United States. Given this diversity of threats, how may Congress and the Department of Homeland Security (DHS) set border security priorities and allocate scarce enforcement resources?
In general, DHS's answer to this question is organized around risk management, a process that involves risk assessment and the allocation of resources based on a cost-benefit analysis. This report focuses on the first part of this process by identifying border threats and describing a framework for understanding risks at U.S. borders. DHS employs models to classify threats as relatively high- or low-risk for certain planning and budgeting exercises and to implement certain border security programs. Members of Congress may wish to use similar models to evaluate the costs and benefits of potential border security policies and to allocate border enforcement resources. This report discusses some of the issues involved in modeling border-related threats.
Understanding border risks begins with identifying key threats. At their roots, border-related threats are closely linked to the flow of people (travelers) and goods (cargo) from one country to another. Any smuggled item or individual hidden among the legitimate flows potentially constitutes a threat to U.S. security or interests.
The intentions and actions of unauthorized travelers separate them into different threat categories, including terrorists, transnational criminals, and other illegal migrants.
Illegal goods are distinguished by their inherent legitimacy or illegitimacy. Certain weapons, illegal drugs, and counterfeit goods are always illegal and categorically prohibited, while other goods are legal under most circumstances, but become illegitimate if they are smuggled to avoid enforcement of specific laws, taxes, or regulations.
The risks associated with these diverse types of threats may be modeled as a function of (1) the likelihood that the threat will be realized, and (2) the potential consequences of a given threat. In practice, however, estimating likelihood and evaluating potential consequences are challenging tasks, particularly when it comes to the diversity and complexity of border threats. Assessing border threats is also difficult because terrorists, criminals, and migrants are strategic actors who may adapt to border defenses. This report describes some of these challenges, and suggests questions policymakers may ask to develop their own "maps" of border risks. Several potential border threats are described, and the report summarizes what is known about their likelihood and consequences.
The report concludes by discussing how risk assessment may interact with border security policymaking. Given the uncertainty and the subjective judgments involved in modeling risk, policymakers may struggle to reach a consensus on border priorities. Nonetheless, a systematic approach to studying border threats may help clarify the types of policy tradeoffs lawmakers confront at the border.