While that's not entirely true, the underlying technology of the system was in part designed with just that scenario in mind.

The Internet traces its origins back to a U.S. Defense Department project during the hottest part of the Cold War. The system was originally conceived of as a way to let computer users attached to disparate networks exchange data with each other.

It was also supposed to be based on a technology that would route information around damaged parts of the network to a safe arrival at its final destination.

Research into developing such a system began with funds from the Defense Department's Advanced Research Projects Agency (ARPA). By 1968, researchers had hooked up the Stanford Research Institute, the University of California at Los Angeles, the University of California at Santa Barbara and the University of Utah under a network known as ARPANET, which eventually evolved into today's Internet.

The magical part of the Internet technology is a bit of software called Transmission Control Protocol/Internet Protocol. Every computer connected to the Internet has some TCP/IP software inside it.

When an e-mail message -- or anything else -- is sent over the Internet, the TCP part of the software dices it up into small units called "packets." The packets are transmitted on the Internet and then reassembled into the original message at the receiving end.

The IP part of the TCP/IP software slaps an address on each packet, to make sure each packet gets to the right destination. Those addresses are read by "routers," the computers that make the data flow through the Internet.

The routers work like the switches on a railroad, shoving traffic onto different tracks, trying to keep packets moving smoothly. If one path gets too crowded, the routers will automatically shift traffic to the next best one; if the main line becomes impassable, the routers will find the next best way to get data to its destination, assuming one exists.

It's that capability that would come in useful in the event of a nuclear attack. If a bomb in the Midwest took out the shortest path between New York and Los Angeles, for instance, the routers would work around it, perhaps sending the data through Florida and Texas to get from coast to coast.

Vinton G. Cerf, who is revered as one of the Internet's creators, says that, theoretically, if properly constructed, the system could remain functional after a nuclear strike.

"We even tested these ideas by simulating the fragmentation of the ARPANET and re-binding it using flying packet radios on Strategic Air Command aircraft in the early 1980s," recalls Cerf, who is now senior vice president for Internet architecture and engineering at MCI Communications Corp. in Washington, D.C.

That simulation, using special radios equipped with Internet technologies, proved that if a nuclear bomb dropped and the network was initially splintered, the remaining sections of the network would seek each other out and relink, continuing to transmit information across the surviving parts of the system.

But Cerf is quick to say that there was no truth to the widespread belief that the Internet, or even its predecessor ARPANET, was impervious to nuclear attack. "That was not true, although its design did make use of the robustness of packet switching to route around failures and congestion."

However, if there's no alternative path the routers can use to get data to locations on a given path, in the event of damage to that path, Internet access will disappear for anyone connected to that path.

For instance, in January 1995, a water pipe broke in a basement at the University of Nebraska at Lincoln. Computer users in seven states lost their Internet access when the minor flood knocked out power to a central Internet hub for Arkansas, Iowa, Kansas, Missouri, Nebraska, Oklahoma and South Dakota.

There are numerous such chokepoints on the Internet, and a single accident, such as a road repair crew cutting an underground cable, can shut down Internet access in a wide area. Engineers would say such a system lacks redundancy; sometimes there aren't enough alternative paths to move data if the main path is closed.

The truth is that, while the Internet has its roots in the Cold War and was a Defense Department project, the system wasn't really designed for war.

"ARPANET was mostly motivated by the desire to allow computing resources to be shared among a dispersed group of users -- in the case of ARPANET specifically, these were computer science researchers at different institutions funded by ARPA," says Cerf. "Of course, the idea could be translated into military command and control scenarios, and that was a principle conceptual motivation for doing the work on ARPANET in the first place."

It's a historical irony that the Internet, a Cold War technology, will likely make its greatest contribution to promoting democracy in a post-Cold War world, allowing the free flow of information into even totalitarian societies.

"Dictators depend upon control of information," says Ira C. Magaziner, who's in charge of developing Internet policy for the White House and holds the title of senior adviser to the president for policy development.

"It's essential in the long term to maintaining a dictatorship, and the Internet makes it impossible ultimately for government to control the information that their people have access to. And I think for that reason it's going to be a tremendous democratizing force."