The driving force behind the Customs-Trade Partnership Against Terrorism (C-TPAT) is the idea that it is possible for private companies to risk-manage for a onetime terrorist event. With the right information about the supply chain and the full cooperation of companies, it will be possible to prevent a terrorist attack, argues former U.S. Customs and Border Protection Commissioner Robert Bonner.

But Stephen Flynn, a national security expert with the Council on Foreign Relations, says that the private sector doesn’t design security systems to prevent events. Instead, companies set up trip wires at vulnerable points and wait until they detect an intrusion. Then they respond.

"No one has failproof security," says Flynn. "I can give a truck driver more money than he will ever see again in his life and tell him he needs to go to lunch for three hours."

While Flynn thinks that C-TPAT is a good program, he believes it should only be part of a broader solution. Instead of focusing solely on preventing an attack, he argues that Customs should be planning how to respond and recover from an attack. Flynn advocates equipping ports with drive-through X-ray, radiation and gamma ray scanners. These might help prevent an attack, but more importantly, scanners could help investigators pinpoint the exact time and place where a bomb was slipped into a container.

"A dirty bomb is a weapon of mass disruption," says Flynn. "Its goal is to disrupt the system." Knowing exactly where the weakness in the system is might allow the rest of the system to carry on normally and avoid a nationwide shutdown.