DHS recently conducted a drill involving a series of mock disasters to test its defenses against hackers. The list of fictional catastrophes included the disruption of airport control towers in Philadelphia and Chicago and bloggers revealing the location of rail cars with hazardous materials. "They point out where your expectations of your capabilities may be overstated," DHS Secretary Michael Chertoff said. "They may reveal to you things you haven't thought about. It's a good way of testing that you're going to do the job the way you think you were."