Twenty years of viruses and still no cure

In a testament to the unpredictable nature of viruses, even Walker guessed wrong about how long his self-replicating creation would last. He recently talked to an administrator of a Unisys 2200 system, a descendent of the UNIVAC computers who reported that the program still runs on his machine.

"It's still looking for file system tables that are 30 years out of date," Walker said.

The host in the machine
Viruses proliferated exponentially with the popularity of desktop computers. Not only did individual computers enlarge the pool of hosts a virus could infect, but they also yielded a new techno-savvy generation armed with the knowledge to create such programs.

Rich Skrenta fit the bill to a tee: a Pittsburgh-area ninth-grader in 1982, he knew a lot about the Apple II and loved to use software to play practical jokes on his classmates. The then-teenager supplied his friends with Apple II programs to which he had added some custom "features", such as the machine's ability to shut down automatically after being used just a few times or to display a taunting message.

"After I had done this a number of times, no one would take games from me anymore," said Skrenta, now the president of his own, soon-to-be-launched search start-up, Topix.net. "And so, I was puzzling on how to get my tricks onto their disks."

That's when he got the idea to write a self-propagating program that would infect Apple II disks. Skrenta's idea for "cloner" programs -- he didn't employ the term virus -- would infect a popular command on the system disks used by the Apple II. The program he created, called Elk Cloner, counted how often a disk had been used and, on every fifth run, made the computer shut down or perform some other "trick." Every 50th time the computer started up, Elk Cloner would display a little poem.

Four years later, two Pakistani brothers, Amjad and Basit Farooq Alvi, created the first computer virus to infect IBM PCs. Known as the Brain virus, the brothers used the program as a piece of true viral marketing: Each copy caused a message to flash on the screen, advertising the brothers' company, Brain Computer Services of Lahore, Pakistan.

"Beware of this VIRUS...Contact us for vaccination," stated the message, which can be found on their Internet site today.

That was only the beginning. Although viruses and worms took more than a decade to emerge in significant numbers, they soared in subsequent years. By the end of 1990, about 200 viruses had been identified. Today, that number has jumped to more than 70,000. Although less than 1 percent of those viruses have compromised computers on the Internet, more than 80 percent of companies suffered a digital infection, according to the Computer Security Institute.

Symantec's Gordon said most virus creators -- not unlike their predecessors -- still don't understand the ability of the programs to spread throughout the Internet. "They tend to be curious -- often articulate individuals with a variety of relationship and interaction styles," she said.

Cohen, however, said the scientific heavy lifting for today's Internet viruses was done in the 1980s. Everything else, he said, is just mechanics.

"Everything that we know now was known then," he said. "Everything we see now is just an engineering solution based on old science."