-- by Lenny Bailes
Computer viruses come in many forms, from relatively harmless pests to intruders intent upon destruction. They're easily and unobtrusively transmitted, and the methods they use to avoid detection nearly match the sophistication of the tools designed to find and eradicate them.
Today, the threat of a virus worming its way into your PC is greater than ever, with the Internet explosion and ever-growing use of e-mail making file swapping an everyday thing.
Antivirus experts have identified and cataloged as many as 10,000 computer viruses. Luckily, PC users have to worry about only 700 of those viruses--the ones known to be in circulation, or "in the wild," in virus-speak. Viruses in the wild are the ones you're most likely to pick up from casually copied floppy disks, poorly managed shareware sites, infected rental PCs and documents transmitted as e-mail attachments.
In past years, new viruses appeared at a clip of about 100 to 150 a year, but in 1996 the proliferation rate approached epidemic proportions. The 1996 Virus Prevalence Survey conducted by the National Computer Security Association (NCSA) revealed that macro viruses carried and spread by documents created with Microsoft Word have become the most prevalent virus type in North America. The Symantec AntiVirus Research Center (SARC) reports that three to six new computer viruses are discovered every day. According to the SARC, since December 1996, researchers have documented 205 Word macro viruses--up from 42 known to exist in August 1996.
The numbers add up to a simple fact: The risk of infection and file damage from computer viruses is significantly greater today than it has been in the past. Previously, most viruses caused relatively little damage with annoying--but nondestructive--symptoms such as messages that flashed across your screen. A handful of viruses were hell-bent on destruction, programmed to corrupt files or partitions, or otherwise separate you from your data. Interestingly, many of these activated themselves only on specific trigger dates--like the famed Michelangelo--so their effects could often be avoided.
Inevitably, the threat of a virus stirs visions of lost, unrecoverable data. While that happens relatively rarely, there is a real--and significant--loss associated with all viruses: lost money. It's the money your company spends to install antivirus software on your PCs and servers. And the impact on productivity costs you plenty, too. Someone has to check and inoculate infected machines, and the users of those PCs aren't likely to be very productive during the process.
To combat viruses effectively, you have to arm yourself with knowledge. You should know the types of viruses out there, the forms they take, how they proliferate on your hard disk and what the most effective remedies are.