What is a computer Virus and how do they work?

Viruses can create a technological holocaust for millions of computers around the world. Businesses fret over the potential for a catastrophic meltdown of networks. Individual consumers worry about zapping their computer's hard drive simply by clicking the wrong e-mail attachment. Experts say such worries are well-founded, but emphasize that a combination of the latest anti-virus software and common sense will drastically reduce the odds of being infected. The cost of not taking such precautions can be high.

"Many people will get a virus at one point or another, and some of them will be harmed by it," said Bruce Peters, a anti-virus and data recovery expert. "Some will lose data, some will suffer no damage other than the time, effort, and stress it takes to remove the virus. Some will spread the virus to others and damage the most valuable thing: their reputations."

Anatomy of a Virus

Though most computer users have learned to fear viruses, few really know what they are. Viruses are programs that replicate themselves inside a computer. The malicious bug cannot do its damage when a user simply surfs the Web or opens a plain text message such as an e-mail. However, viruses are unleashed when they are hidden in attachments to e-mail messages and someone opens that attachment. After viruses replicate, many carry out damaging instructions that have been programmed into them.

The Melissa virus from March 1999 is a good example of how viruses inflict damage. Melissa lurked inside an e-mail Microsoft Word attachment. The person who received the message had no reason to suspect anything dangerous; in fact, the e-mail's subject line appeared to be from someone the recipient recognized.

However, once the recipient clicked on the attachment, Melissa fused itself to a Word object and began rifling through the poor victim's address book. Soon, Melissa was e-mailing tainted attachments to the first 50 names in the recipients address book.

"Some viruses do nothing except replicate," Peters said. "Some will do damage, but not intentionally. Then again, there are those that attempt - and sometimes succeed - in destroying all files on the computer, or subtly altering data in documents, or whatever nasty thing you can conceive that a computer program is capable of doing."

To make matters worse, those who create viruses continually add new twists to their method of attack. Late in June, the Stages virus struck. Before Stages, computer users were assured that viruses could not be spread through text files. So, when Microsoft Outlook users saw an attachment that appeared as "LIFE_STAGES.TXT," many figured it was safe to open. When they did so, a humorous test file about dating appeared.

What users didn't realize was that the attachment was not a text file but had a hidden .SHS extension, which meant it contained infected computer code. Soon, the virus was on the loose and e-mailing itself to everyone in the recipient's address book.

Protect Yourself

There are a few basic rules that computer users should follow to short-circuit viruses. The best known bit of advice is this: Never open any attachment unless you know who it's from and why they are sending it. Peters said refusing to open unsolicited e-mail of any kind is the only sure-fire way to sidestep all forms of trouble.

Anti-virus software is crucial to preventing virus attacks, but this strategy only works if users update their software, Peters said.

"Unfortunately, 'keeping it current' means updating it weekly, at least," Peters said. "Most products today allow one to automate this process, but file downloads can be large and slow."

Factors to consider when buying an anti-virus package include cost, quality of tech support, how frequently the package self-updates and the platforms supported by the program, Peters said.

Common sense is another good weapon in the fight against viruses. Peters says you should request that those who send you attachments precede it them with an e-mail describing what is to be sent, so you'll be ready for it. Make sure you ask your sender to scan all attachments for viruses before the e-mail is sent to you, he said.

He also suggests setting up your anti-virus product so that it automatically scans incoming e-mail and avoiding e-mail software that allows automatic launching of attachments.

If all of this sounds like a lot of work, it is. As Peters says, "there is always a tradeoff between ease of use and security," but he believes it is crucial to work toward "maximizing the latter." For example, the extra time you spend updating your anti-virus software now will save you hours of time and buckets of frustration later, he said

"If you don't keep it updated, you might was well be completely unprotected," Peters said.

Help on the Web

The WildList Organization International (www.wildlist.org) offers a list of viruses that are floating through the computer world at present. The site also offers the opportunity to report viruses, should you be unfortunate enough to encounter a new one firsthand.

Peters's suggestions include the Virus Bulletin (www.virusbtn.com) and its Virus Bulletin 100% Awards, which recognize products that excel at detecting viruses.

Peters hopes the recent wave of high-profile viruses will cause lawmakers to treat the problem as the potentially serious crime that it is. However, he said the war on this scourge requires vigilance.

"Yes, we'll become more successful overall," he said. "But yes, things will get worse, too: my prediction is that while more viruses will be prevented on a percentage basis, there will always be a few high profile successes by the virus writers.

"Those successes, however, will be short-lived, because anti-virus companies will be quick to create a solution to each new threat."