The computer virus turns 25

The computer virus turns 25 years old this year. It's been a rocky quarter-century, but according to Richard Ford and Eugene Spafford, two computer scientists writing in this week's issue of the journal Science, viruses can look forward to a long, fruitful life. The researchers say that in today's hyper-connected world, when everything's got a chip in it and is running software, stopping malware is basically an impossible task. (Their article is not online.)

The computer virus conception story begins in 1981, when a tech-savvy 9th grader named Richard Skrenta got an Apple II for Christmas. Over the following few months he began cooking up ways to trick his friends using the machine. "I had been playing jokes on schoolmates by altering copies of pirated games to self-destruct after a number of plays," Skrenta once told the tech news site Security Focus. "I'd give out a new game, they'd get hooked, but then the game would stop working with a snickering comment from me on the screen."

When his friends realized his tricky ways, they banned Skrenta from their machines. And that's when he had an epiphany: He could put his code on the school's computer, and rig it to copy itself onto floppy disks that students used on the system. Thus was born Elk Cloner, the world's first computer virus to spread in the wild. The virus didn't do much damage; it infected the Apple II's OS and copied itself to other floppies, and every so often would display a tittering message on the screen:

Ford and Spafford note that in the years since, as viruses spread to other computer platforms and throughout the world, wreaking billions in damages, there has been little progress in fighting them. There is a scientific reason for this: "Building a computer program that can tell with absolute certainty whether any other program contains a virus is equivalent to a famous computer science conundrum called the 'halting problem,'" they write. The halting problem concerns the difficulty of spotting whether a program will terminate or continue to run forever. "It has no solution in the general case and has no approximate solution for our current computing environments without also generating too many false results," they write.

Ford and Spafford also take on the idea that Microsoft is to blame for our current virus ills. Certainly MS has neglected to secure Windows, but any platform that obtains ubiquity will become a target for attack, they note. Some say the solution is to have a diverse computing environment -- if the world ran all kinds of different platforms, rather than a Windows monoculture, viruses would spread much less slowly. But diversity, Ford and Spafford point out, creates its own problems -- if the Mac, Linux and Windows all had roughly equal share, you'd need anti-virus teams working to protect all three platforms, any one of which could serve as a weak point for wider network destruction. Platform diversity, that is, increases the "attack surface," they write.

Worse still is the potential for completely computer-free computer viruses. They point to a chain e-mail message that counseled people to delete a particular file from their computer to keep it secure. "The file they deleted was critical to the system," it turned out. The "virus" that caused its deletion was "executing" only in people's minds. And you can't get a virus checker for the brain.

So right: Happy birthday, computer virus. Many happy returns!