Terrorism is a new and different thing in the age of the Internet. While rumors get started in many ways, they didn't spread much before internet unless they reached the level of a urban myth (with no specifics). But with internet, everything is different. Any rumor is now heard the same day by several million Americans instead of a few dozen, and a whole class of people who make up rumors just to see them spread has arisen. Hundreds of rumors have appeared. Anthrax is known in a few cases by the Centers for Disease Control, but has reported in dozens of localities by denizens of cyber chat rooms and news groups. A man with a jar of some biowar agent was wrestled to the ground at a train station, but the same story (repeated on internet) took place in a dozen train stations. Numerous rumors have some basis in fact. Reports circulated that 30 rental trucks had been stolen over one weekend, which was true (but about the average number of late returns and truly stolen vehicles); reports that all 30 were rented by "Middle Eastern men" could never be confirmed. Everyone who is even vaguely Arab-looking can spark a dozen rumors of terrorists surveying possible targets just going about his normal business. A group of Arab engineers visiting the US showed no interest in a group of Native American ruins in the West, but were fascinated by a nearby dam (not surprising, since they were engineers not archaeologists), sparking rumors of an impending attack on the water supply of a major city.--Stephen V Cole