All About Computer Viruses


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Date of copyright: November 2004

All About Computer Viruses
by Kara Glover

Your computer is as slow as molasses. Your mouse freezes every 15 minutes, and that Microsoft Word program just won?t seem to open.

You might have a virus.



In comparison, there are pieces of code that might replicate inside your computer, say something your IT guy thinks you need. But the code spreads, perhaps throughout your office network, with your consent (or at least your IT guy?s consent). These types of replicating code are called agents, said Jimmy Kuo, a research fellow with McAfee AVERT, a research arm of anti-virus software-maker McAfee Inc.

In this article, though, we?re not talking about the good guys, or the agents. We?ll be talking about the bad guys, the viruses.




Because so many other types of viruses exist now, the kind just described is called a classic virus. Classic viruses still exist but they?re not quite as prevalent as they used to be. (Perhaps we could put classic viruses on the shelf with Hemingway and Dickens.)


As far as web browsers are concerned, Microsoft?s Internet Explorer takes most of the heat for spreading viruses because it?s used by more people for web surfing than any other browser.

Nevertheless, ?Any web browser potentially has vulnerabilities,? Nachenberg said.

For instance, let?s say you go to a website in IE you have every reason to think is safe, Nachenberg said.

But unfortunately it isn?t. It has virus code hidden in its background that IE isn?t protecting you from. While you?re looking at the site, the virus is downloaded onto your computer, he said. That?s one way of catching a nasty virus.

During the past two years, another prevalent way to catch a virus has been through downloads computer users share with one another, mostly on music sharing sites, Kuo said. On Limewire or Kazaa, for instance, teenagers or other music enthusiasts might think they?re downloading that latest Justin Timberlake song, when in reality they?re downloading a virus straight into their computer. It?s easy for a virus writer to put a download with a virus on one of these sites because everyone?s sharing with everyone else anyway.



Forget opening the attachment. All you have to do is view the email to potentially get a virus, Kuo added. For instance, have you ever opened or viewed an email that states it?s ?loading?? Well, once everything is ?loaded,? a virus in the email might just load onto your computer.

So if I were you, I?d click on View on the toolbar in your Outlook or Outlook Express and close the preview pane. (You have to click on View and then Layout in Outlook Express.)



OK, so we?ve talked about how the viruses get into a computer. How do they cause so much damage once they?re there?

Let?s say you?ve caught a classic virus, one that replicates and attacks various files on your computer. Let?s go back to the example of the virus that initially infects your Microsoft Word program.

This process of infecting targets and looking for new ones could eventually use up your computer?s ability to function, he said.


There are other potential reasons, though, for a virus to cause your computer to be acting slow or in weird ways. And that leads us to a new segment ? the reason virus writers would want to waste their time creating viruses in the first place.


For these other intentions, we first need to explain the ?backdoor? concept.



Trojans are pieces of code you might download onto your computer, say, from a newsgroup. As in the Trojan War they are named after, they are usually disguised as innocuous pieces of code. But Trojans aren?t considered viruses because they don’t replicate.

Now back to the real viruses. Let?s say we have Joe Shmo virus writer. He sends out a virus that ends up infecting a thousand machines. But he doesn?t want the feds on his case. So he instructs the viruses on the various machines to send their signals, not of course to his computer, but to a place that can?t be traced. Hotmail email happens to be an example of one such place, Kuo said.



Ever heard of phishing emails? Those are the ones that purport to be from your internet service provider or bank. They typically request some information from you, like your credit card number. The problem is, they?re NOT from your internet service provider or your bank. They?re from evil people after your credit card number! Well, these emails are often sent the same way spam is sent, by sending them via innocent computers.



?2004 by Kara Glover

About the author:

Kara Glover is a Computer Tutor and Troubleshooter. You can find her articles and tutorials on topics such as Microsoft Word?, Excel?, and PowerPoint? on her website:

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