Port security improvements are needed due to the inherent vulnerability of ports to terrorist attacks. Ports are vulnerable because of their size, generally open accessibility by water and land, location to metropolitan areas, the amount of material being transported through them, and the ready transportation links to many locations within U.S. borders.

Since ports have many different transportation modes (e.g., rail, roads, & water ways), they are more open to terrorist attacks than many other areas. The large concentration of passengers, cargo, property, and businesses at or near ports make them potential targets. As a result, a major terrorist attack with nuclear, chemical, biological, or radiological weapons would result in extensive loss of lives, property, and business.

In addition, essential trade to the U.S. would be severely impeded. Not only would the port be affected, but so could the transportation infrastructure (bridges, railroads, and highways) within the port limits. The Brooking's Institution reported in 2002 that a weapon of mass destruction shipped by container or mail could cause damage and disruption by as much as $1 trillion.