Computer Virus 101
Article by Rick Leinecker, February 20, 2006

This article is the second in a new series about computer security. I'm targeting the average person, so I won't get too technical. My intention is to provide good and useful information for home and business users that'll help keep their computers safe. Today, we'll be talking about computer viruses.

Similar to viruses that your body catches, computer viruses do harm to computers. Unlike the common cold, a computer virus can't survive without a host such as a program or document. Computer viruses are "caught" with an action taken by the computer operator such as opening an infected program. (One exception to the previous statement is in the case of worms which we'll talk about in a few weeks.)

You may remember from last week, I mentioned that SpyWare surreptitiously compromises computers for the benefit (usually financial) of a third party. Viruses compromise computers in a similar way, but not usually for financial reasons. The main purpose of a virus is to do harm to your computer. This harm takes many forms including deleting important or essential files.

Computer viruses live just to wreak havoc. Sometimes they lie dormant for days, weeks, or months coming out of hibernation when least expected. The wait gives them a chance to infect other files so that offspring infect other computers. The wait also allows some viruses to synchronize their effect worldwide and maximize the shock and effect.

At this point you have to be asking "why in the heck would anyone write a virus?" And you wouldn't be alone asking that question. There are lots of reasons including sociopathy, revenge, the challenge, and as a learning exercise. With all of the millions of talented programmers in the world, it's no wonder that a small number have an axe to grind with society, an organization, or a particular person and are driven to create viruses.

The Melissa virus may be the most famous. Within three days it had spread to hundreds of thousands of computers, and many email servers had to shut down. Melissa, by the way, was a stripper in Miami who the virus author had a liking for.

The "I Love You Virus" was pretty famous, too. It searched hard drives for passwords and sent them to a location in the Philippines.

Some virus threats are hoaxes. I often get warnings via email about the next greatest virus. Many of these aren't true. Before you get overly excited about an imminent threat, check a reliable source to see if it's authentic. I usually go to, click on the "Latest Threats" link, and then search for the threat.

Just like colds and other human viruses, computer virus prevention is important. There are several ways to get computer viruses. The most common is running a program that either is or contains a virus. Sometimes programs that you normally use can become infected unbeknownst to you. Many times infections arrive as email attachments. Don't ever open a program that's an email attachment unless you explicitly trust the source.

Very often files that are traded over peer-to-peer sharing programs (that your kids may be using) are infected. They might promise to speed up your computer, give you a registration key for commercial software, or any number of tempting outcomes. But you may end up paying way more than you expect because they can do just about anything to your system including deleting and corrupting essential files.

Files such as Microsoft Word or Microsoft Excel files that contain macros may contain threats. Macros are similar to programs since they can potentially perform undesirable operations on your computer. Besides being careful about what programs you run, be careful what documents you open.

In addition to prevention, you can inoculate your computer against viruses. Unlike the current SpyWare inoculation programs, virus inoculation programs are practically seamless and you won't even notice them. The four I recommend are Norton (, McAfee (, PC-cillan (, and AVG ( Of these four, AVG is free.

Anti-virus programs update their definitions on a regular basis. Make sure that you have the software set to either automatically download definition updates, or that you do it manually on a regular basis. The updated definitions let the software know how to deal with the latest and greatest known threats.

Also important is to make sure that the "auto-protect" feature is turned on. This insures that any virus that attempts to run or infect your system will be immediately thwarted.

The third component of anti-virus use is regular system scans. These examine the memory and files of your computer, and can catch problems that auto-protect somehow missed. I schedule scans for 3AM on my computers. But the anti-virus software is flexible and gives you a wide range of scheduling options that help meet your specific needs. You can also manually do system scans.

Those are the basics of Computer Viruses.