A decade ago there was a lot of talk about how vulnerable the United States was to a terror attack via shipping container. It never happened. It’s also unlikely because of the large number of variables the terrorists face. The problems associated with using cargo containers to move a nuclear or conventional bomb are manifold. The big problem is that these containers often don’t arrive right on schedule. Sometimes the ship breaks down or encounters bad weather. This last event leads to thousands of containers a year falling off cargo ships and going to the bottom with their cargo. Sometimes containers get lost “in the system.” More frequently containers get robbed or opened by mistake. Customs officials open a small percentage (this varies by port) for inspection. Another problem, whether the bomb goes off or not, is the fact that containers have to have documentation like bills of lading and such. These can be faked, but the problem is that a paper trail is being created and that can lead to terrorists getting arrested. All containers must officially belong to someone, they are tracked and any that aren't being tracked tend to get noticed. Many countries do scrutinize containers coming from certain countries in an attempt to catch people smuggling drugs or arms. Large bombs, be they nuclear or conventional, are relatively fragile and may not survive (in working condition) the punishment received during a long sea voyage. If all that weren’t enough to make terrorists nervous, container ships can be delayed when trying to enter a port because of congestion. This can delay arrival by days or even weeks.
The terrorists have one major advantage here. It was noted a decade ago, U.S. Homeland Defense planners began wondering how they could possibly examine six million containers a year. Each year, over 50,000 ships were entering American ports back then and dropping off these six million containers. Although there are 361 seaports in the U.S., 25 of them account for 98 percent of the container traffic. Taking advantage of this concentration of activity, intelligence collecting activities were concentrated on these ports and on the overseas ports from which the containers were shipped. Using profiles of known terrorists and the composition of the work force in places that load containers headed for the U.S., it was possible to narrow down the number of likely sources of containers with weapons or other materials terrorists might use. This made it possible to get the most out of limited information collecting resources. Keeping an eye on containers isn't enough, however, because there's also the possibility of chemical, biological, or nuclear weapons being put in a container and then detonated before the ship can dock and have its containers examined. This is another reason why the intelligence effort is moving overseas to the shipping ports, not the receiving ones in the United States.