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Someday the Internet may become an
information superhighway, but right now it is more like a 19th-century railroad that
passes through the badlands of the Old West. As waves of new settlers flock to cyberspace
in search for free information or commercial opportunity, they make easy marks for
sharpers who play a keyboard as deftly as Billy the Kid ever drew a six-gun.
It is difficult even for those who ply it
every day to appreciate how much the Internet depends on collegial trust and mutual
forbearance. The 30,000 interconnected computer networks and 2.5 million or more attached
computers that make up the system swap gigabytes of information based on nothing more than
a digital handshake with a stranger.
Electronic impersonators can commit slander
or solicit criminal acts in someone else´s name; they can even masquerade as a trusted
colleague to convince someone to reveal sensitive personal or business information.
"It´s like the Wild West", says Donn B. Parker of SRI: "No laws, rapid growth and enterprise - it´s shoot first or be killed." To understand how the Internet, on which so many base their hopes for education, profit and international competitiveness, came to this pass, it can be instructive to look at the security record of other parts of the international communications infrastructure. The first, biggest error that designers seem to repeat is adoption of the "security through obscurity" strategy. Time and again, attempts to keep a system safe by keeping its vulnerabilities secret have failed. Consider, for example, the running war between AT&T and the phone phreaks.
When hostilities began in the 1960s, phreaks could manipulate with relative ease the long-distance network in order to make unpaid telephone calls by playing certain tones into the receiver. One phreak, John Draper, was known as "Captain Crunch" for his discovery that a modified cereal-box whistle could make the 2,600-hertz tone required to unlock a trunk line. The next generation of security were the telephone credit cards. When the cards were first introduced, credit card consisted of a sequence of digits (usually area code, number and billing office code) followed by a "check digit" that depended on the other digits. Operators could easily perform the math to determine whether a particular credit-card number was valid. But also phreaks could easily figure out how to generate the proper check digit for any given telephone number.
So in 1982 AT&T finally put in place a more robust method. The corporation assigned each card four check digits (the "PIN", or personal identification number) that could not be easily be computed from the other 10. A nationwide on-line database made the numbers available to operators so that they could determine whether a card was valid. Since then, so called "shoulder surfers" haunt train stations, hotel lobbies, airline terminals and other likely places for the theft of telephone credit-card numbers. When they see a victim punching in a credit card number, they transmit it to confederates for widespread use. Kluepfel, the inventor of this system, noted ruefully that his own card was compromised one day in 1993 and used to originate more than 600 international calls in the two minutes before network-security specialists detected and canceled it.
The U.S. Secret Service estimates that stolen calling cards cost long distance carriers and their customers on the order of 2.5 billion dollars a year. During the same years that telephone companies were fighting the phone phreaks, computer scientists were laying the foundations of the Internet. The very nature of Internet transmissions is based on a very collegial attitude.
Data packets are forwarded along network links from one computer to another until they reach their destination. A packet may take dozen hops or more, and any of the intermediary machines can read its contents. Only a gentleman´s agreement assures the sender that the recipient and no one else will read the message. But as Internet grew, however, the character of its population began changing, and many of the newcomers had little idea of the complex social contract. Since then, the Internet´s vulnerabilities have only gotten worse. Anyone who can scrounge up a computer, a modem and $20 a month in connection fees can have a direct link to the Internet and be subject to break-ins - or launch attacks on others.
The internal network of high-technology company may look much like the young Internet - dozens or even hundreds of users, all sharing information freely, making use of data stored on a few file servers, not even caring which workstation they use to accessing their files. As long as such an idyllic little pocket of cyberspace remains isolated, carefree security systems may be defensible. System administrators can even set up their network file system to export widely used file directories to "world" - allowing everyone to read them - because after all, the world ends at their corporate boundaries. It does not take much imagination to see what can happen when such a trusting environment opens its digital doors to Internet. Suddenly, "world" really means the entire globe, and "any computer on the network" means every computer on any network. Files meant to be accessible to colleagues down the hall or in another department can now be reached from Finland or Fiji.
What was once a private line is now a highway open to as much traffic as it can bear. If the Internet, storehouse of wonders, is also a no-computer´s land of invisible perils, how should newcomers to cyberspace protect themselves? Security experts agree that the first layer of defense is educating users and system administrators to avoid the particularly stupid mistakes such as use no passwords at all. The next level of defense is the so called fire wall, a computer that protects internal network from intrusion. To build a fire wall you need two dedicated computers: one connected to the Internet and the other one connected to the corporation´s network. The external machine examines all incoming traffic and forwards only the "safe" packages to its internal counterpart. The internal gateway, meanwhile, accepts incoming traffic only from the external one, so that if unauthorized packets do somehow find their way to it, they cannot pass.
But other people foresee an Internet made up mostly of private enclaves behind fire walls. A speaker of the government notes, "There are those who say that fire walls are evil, that they are balkanizing the Internet, but brotherly love falls on its face when millions of dollars are involved". In the meantime, the network grows, and people and businesses entrust to it their knowledge, their money and their good names.
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