Computer viruses - how computers get sick and how to cure them - includes related articles

Science World, Oct 19, 1998 by Michael Cannell

Do computers get sick? You bet. They laid low--by a virus!

You switch on your computer, eager for it to boot up so you can join thrill-seeker Lara Croft as she searches for the ancient Emperor's palace in the Great Wall of China in Tomb Raider II. Wait! Where's the familiar green screen? Something's wrong. Ding! Whrrrr! Crrrrrash! You turfi off the computer, then on again. This time--NOTHING.

What happened?

Your computer has just been zapped by a computer virus--a malicious program that at worst could wipe out all your computer files. Gone is your dog Frosty's photo. Gone is Lara. And erased is every homework assignment, including the American History term paper that took a week to grind out.

Could this really happen to you? You bet. And getting a computer virus has become much easier than before.

NASTY NEWS

As recently as five years ago, a virus could spread from computer to computer mainly through shared floppy disks. Now, just opening up your electronic mail, or e-mail, can launch a nasty virus into your system.

Last summer, headlines proclaimed that widely popular e-mail programs like Microsoft's Outlook 98 and Outlook Express, as well as Netscape Mail, and Qualcomm's Eudora, are vulnerable to virus attacks. "You can get an e-mail that looks like any other e-mail," explains Alex Haddox, head of Symantec AntiVirus Research Center in Santa Monica, California. "Except when you open up the e-mail itself, by the time you read it, it's too late." You've got a virus!

Who would perpetrate such a potentially harmful trick? Virus writers are mostly males age 14 to 24. For these digital delinquents, unleashing a new virus is an ego trip, says Haddox: "'Can I do it? Can I push the limits of technology?' Their greatest thrill is to have their name or their virus posted in the news worldwide."

One 26-year-old British virus writer who identifies himself only as Rajaat admits, "I do get personal gratification out of it. For me, it's a challenge to see if I can outsmart antivirus software, and to try to think of innovative ways to do this."

NO EASY TRICK

Creating a computer virus is no easy trick. Just like computer games and word-processing software, a virus is a program--step-by-step instructions that tell a computer what to do. Unlike games and other software, however, a virus attaches itself to other programs in your computer. "It's essentially a digital parasite," explains Haddox.

A virus contains instructions that tell it to self-replicate, or copy itself over and over again. When it first enters your computer--through an infected floppy disk, e-mail, or a program downloaded from the Internet--the virus copies itself to your computer's memory (see computer diagram, below). From there, it attaches itself to any program you open up. "The virus actually rewrites a program to incorporate itself into the program," says Haddox. "It rewrites the program so the virus will run first."

Every time you open up another file or program, the virus plants itself into that file and takes over. In the process, it can cripple your machine's ability to find the files it needs to start up or operate. The infection doesn't end there. A computer virus, like the common cold, is highly contagious. Its primary purpose is to spread to as many computers as fast as possible, says Haddox.

Computer virologists, programmers who try to combat the digital plague, say 10 to 15 new viruses are launched every day. The virus population, currently about 18,000, nearly doubles every year. Today, the sneaks invade 35 of every 1,000 computers each month. (About 200 million personal computers are in use today.) And thanks to the Internet, the "information superhighway" that connects computers worldwide, outbreaks go global in just weeks or less. With Internet usage exploding, the average user is now 20 times more likely to contract a computer virus.

COMPUTER PERIL

Most viruses are actually harmless, merely displaying silly messages ("I feel good!") or tunes ("Yankee Doodle Dandy") when you boot up. But destructive viruses have swelled to 35 percent of all computer invaders, up from 10 percent just six years ago. The worst of them garble data, hinder printing, or wipe out entire hard drives. The most common computer culprit is the macro virus--a type of virus that infects data documents like letters and spreadsheets--which accounts for more than 80 percent of all computer viruses. A macro is a legitimate mini-program, or procedure list, embedded in popular wordprocessing and spread sheet software, like Microsoft Word and Excel. It enables a user to write a simple program that executes a series of commands within a document, like automatically adding up numbers and presenting a total. Because macros were meant to be written by the average computer user, they're very easy to learn.

"I call the macro virus the `every man's virus'," Haddox says, Anyone with ill-intent can easily write a virus using macros. In fact, one macro virus, called Format_C, formats, or erases, your hard drive with just three lines of instructions.