Stopping terrorists involves first detecting them. To this end, the U.S. Department of Defense has developed a system that identifies vehicles via a "fingerprint", and then tracks the use of each vehicle as it moves past a network of video cameras. The unique "fingerprint" for each vehicle is the color, size and number of wheels on it. This information is collected by video cameras. The digital image is examined by the identifying software, and the database is checked to see if the vehicle has been seen before. Naturally, the cameras track vehicles by time and location. These CZTS (Combat Zones That See) systems are installed at all U.S. bases in Iraq. Attempts to fool the system are very difficult (and the CZTS developers aren't discussing the issue any further, for obvious reasons). CZTS gives troops the same type of information police in the United States have had since the introduction of automatic electronic payment of tolls on bridges and highways.