When your Internet service goes down, it's at best an inconvenience. If you rely on it for business, it can quickly cost you money.
Picture people wandering the streets lost without GPS or maps on their iPhones, unable to pay for food or other goods with a simple swipe of a card.
Companies would have to resort to faxes and phone calls instead of e-mail; they'd quickly reach capacity and be unable to function. Credit cards wouldn't work; stores and hospitals would run short of supplies. Even electrical power to our homes could be disrupted.
"It would be a mess," said Dave Marcus, the director of security research for. "You would be taking businesses that were designed to do all their point-of-sale and financial transactions through the Internet and going back to pen and paper and taking checks in a car to the bank. People would lose their minds."
On the 40th anniversary of the first transmission over the earliest version of the Internet, it's more than an idle question to examine the network's fragility. It's been more than 20 years since the last systemwide overhaul, and Internet infrastructure is still based on 1970s ideas about computer networks.
Headline-making outages of popular Web sites such as YouTube and Twitter merely hint at the damage a full-blown failure could wreak. The Internet protocols that allow computers to communicate in networks have infiltrated every sector of our economy.
"The Internet has moved from being a toy or ornament to something that's central to our economy," said James Lewis, a senior fellow at CSIS, a nonprofit think tank in Washington, D.C. "We've automated all these processes, which makes our economy much more efficient, which means cheap. But it also means we're now dependent."
How could the Internet break?The obvious question is, could it happen? In fact, parts of the Internet go down quite frequently.
The outages that make headlines usually involve a large segment going down, either cutting service to a geographical area or taking down a given Web site. For instance, Michael Jackson's death sent people flooding to sites such as Google News and Twitter, rendering each temporarily inaccessible. A few years ago, Pakistan's attempt to block access to YouTube in that country resulted in a two-hour outage of YouTube across the world. And early this year, hackers kicked the entire nation of Kyrgyzstan off the Internet.
Those examples highlight the two main risks: an attack or a technical collapse.
A systemwide outage is hard to envision, though. The Internet is a decentralized system of routers and networks owned by a variety of governmental and private organizations. That makes it resilient: If one section breaks, the network calculates a route around the disruption.
The Internet opened for business in 1969, when a government project connected scientists, researchers and military officials by networking giant mainframes. In the early 1990s, the government opened the Internet to commercial development. In 1994, Netscape launched its browser, the first of an ever-increasing cascade of user-friendly software and applications for public consumption.
To bring down the entire Internet, something or someone would probably have to disrupt the core Internet protocols -- the rules that computers follow when trying to communicate with other computers. That would not only break the World Wide Web but also private IP networks that companies maintain for greater security.
One possible avenue would be to attack the domain name system, or DNS, that identifies the address of each computer or device attached to an IP network. Currently, just more than a dozen computers scattered around the world contain the DNS addressing information for the entire Internet, Lewis said.
If someone were able to erase or scramble that information, your computer wouldn't know where to find the information on a given Web page or where to deliver an e-mail. But all that information is duplicated on each of the central servers.
Simply staying ahead of the demand for DNS addresses and server capacity is a challenge. VeriSign receives 50 billion queries each day from computers looking for DNS data and expects that to rise to 4 trillion by 2020, according to Ken Silva, the company's chief technology officer.
Part of the debate in Washington over so-called net neutrality involves who would pay for billions in upgrades to enable the Internet to handle the demand of uses such as high-definition video. Experts at AT&T and elsewhere have suggested the Net could run out of capacity next year. The point is hotly debated, and it's not clear what would happen if it did.