Wire Pirates

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 ...