The U.S. Cyber Consequences Unit, a government-sponsored think tank, has concluded that hackers conceivably could crash trains, cause chemical spills, and darken the electrical grid. No such disaster has occurred in the United States, but the number of probes is growing.

As more utilities and industries link their computer networks to the Internet, shadowy adversaries regularly probe the control systems that run crucial infrastructure, officials said during a tour of the cyber-security unit at the Idaho lab, long one of the nation's top nuclear research facilities.

SOURCE:

http"//www.latimes.com/news/nationworld/nation/la-na-idaho-cyber-20111001,0,6859511.story

The above excerpt from an LA TIMES article has me wondering. Could a hacker override the interlocking mechanisms and set up a head-on collision course between two trains with "false clear" signal indications?

Any computer and/or signaling specialists here?

Or, on the other hand, could this just be more manufactured sabre-rattling by the powers-that-be to keep us perpetually scared? For that, see Michael Moore's Bowling For Columbine.