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America's transportation systems include 450 commercial airports, 600,000 bridges, 4 million miles of roadway and 140,000 miles of active railroad, and all of our subways.
The New York City subway, for example, which carries more than 8 million riders each day, uses scores of complicated control systems that could fall prey to hackers.
A real world example: In 2003, the Sobig virus and similar computer worms wreaked havoc on million of computers, shutting down trains on the east coast of the U.S. and Canada and infecting CSX Corp.'s train system headquarters in Jacksonville, Fla. Train service was shut down or delayed up to six hours.
5. Transportation