Fighting off worms and other PC invaders

Sept. 4 started out as a normal workday for Kevin Ma. By noon it was pure chaos.

The Blaster computer virus had taken down corporate computer networks across the country, and Mr. Ma, a computer consultant for Microtech Services in Boston, was among those charged with containing the virus, limiting its damage, and wiping it out.

Blaster, which Ma says "hammered" him and his colleagues, was one of 52 new viruses discovered this month, five of them major.

If you're like most computer users, you don't have Ma to come to rescue your home computer from the hundreds of damaging programs with names like Blaster, SoBig, Lovegate, and Klez.

And with high-speed Internet access linking millions of Americans, home computers are more vulnerable than ever.

Since viruses multiply exponentially through as many computers as possible, enlisting home users to stop their spread is crucial to reducing the overall impact of viruses, says David Perry, global director of education at TrendMicrosystems, an Internet-security company in Orange, Calif.

For all the disruption on corporate networks this month, businesses are generally much better protected than home users, says Mr. Perry.

In fact, the computer that took down the Microtech Services network was a laptop that had picked up a virus on the user's home network.

When dealing with viruses, there is no substitute for knowing what to watch out for and how to keep your computer current. "It's no different from knowing 30 years ago whether your car needed regular or unleaded gas," says Perry.

A few basics:

• A "virus" is simply any piece of computer code that automatically replicates itself. "The vast majority of dangerous content comes as e-mail attachments," says Chuck Adams, chief security officer with Netsolve, a computer-security firm in Waltham, Mass. They can also come through contact with Web pages.

• A "trojan" is an e-mail designed to trick users into opening it and launching a virus. Most often these, too, come as e-mail attachments. Though most Internet service providers now block the most dangerous attachments, experts warn against opening any attachment from an address you don't recognize.

• A "worm" is a more malicious type of computer code, because it doesn't require a user to do anything. Any time a computer is on the Internet, a worm can get in and run, causing anything from so-called "denial-of-service attacks" that bring the Internet to its knees, to deleting all the data on your hard drive.

Unfortunately, staying safe from computer viruses is now largely a reactive process, says Perry. Software companies such as Microsoft fix security holes after they discover them, and distribute the fixes, usually within hours. Corporate servers are designed to automatically look for these patches and install them. Home users should set their operating systems to do the same.

Good virus protection starts with installing antivirus software from one of the big three antivirus companies: Norton, McAfee, and TrendMicro. For anti- virus software to do any good, it has to have up-to-date virus definitions, which means you have to pay for the software and a subscription to keep receiving the latest list of viruses. A disk borrowed from your uncle or grandson probably won't help.

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