The U.S. maritime transportation system consists of hundreds of ports that receive container shipments daily from countries around the globe. Because container shipping is essential to global commerce yet leaves the nation vulnerable to terrorist attack, the United States has installed measures to ensure the security of our ports and reduce our vulnerability due to cargo shipping. A large cargo ship can contain hundreds of containers, which poses challenges for inspectors, as they are restricted from hindering the movement of goods. Also, inspecting large numbers of containers delays the movement considerably.

The U.S. Department of Homeland Security controls port security, which it entrusts to a number of agencies, including CTPAT, the Customs Trade Partnership Against Terrorism. CTPAT is a network of partners that include importers and exporters, transportation intermediaries, highway, rail, and sea carriers, port officials, and others involved in the cargo shipping industry. These partners agree to certain practices that have been put in place to prevent terrorism. For this reason, CTPAT helps prevent terrorism by including groups of people who combine forces to prevent it. Because CTPAT members are considered low risk, cargo shipments that are moved by these organizations are less likely to be tampered with, less likely to be inspected, and less likely to be delayed. CTPAT emerged in the wake of the terrorist attack on the World Trade Center on September 11, 2001, in an attempt to ensure the integrity of incoming cargo.