One thing that is really giving counter-terrorism officials nightmares is the twenty million freight containers that are in use. Seven million of them pass through the United States each year, and currently only two percent of them get any kind of inspection. While theres lots of new technology (electronic tags, and sensors that can detect dangerous contents) on the way, it will be several years before all those spiffy, and expensive, gadgets arrive in large enough quantities to make a difference. Meanwhile, increased efforts at checking containers has revealed that these large metal boxes are already being used to smuggle all sorts of stuff (and people). Some of this smuggling was already known, but the closer counter-terrorism experts look, the more of it they discover. The problem is that the container using smugglers dont really care about what they are paid to move through the global shipping container system. The attitude seems to be, you pay me the money and I will move the goods. While no smuggler wants to get involved with terrorists (which would bring down more police heat that is safe for a smuggler), it would be relatively easy for a terrorist to pass himself off as just another criminal wanting to move goods illegally into the United States. The best defense against this appears to be keeping a close watch on Middle Eastern and Asian ports terrorists are likely to operate from, and terrorist networks in general. Far from perfect, its all thats available for now.