Ever get a virus? And no, we're not talking about the kind you get from the kid down the street sneezing all over you. We're talking about the kind you get when your computer runs into some nasty vindictive hackers. These are people who have nothing better to do with their time but make other people's lives miserable. If you've ever been attacked by one of these things you know what I mean.

Enter the anti virus software. In short what this software does is detect a virus either on your computer or one that is threatening to slice your PC into little bits and bytes. The most popular anti virus software companies are McAfee and Norton Anti Virus, the latter actually owned by Symantec. There are other companies and now even some ISPs like AOL are providing anti virus software. But McAfee and Norton are still the kings of the industry. Before you can understand how anti virus works you have to understand how the virus itself works and how it infects your computer.

Contrary to what people believe there are other ways to get a computer virus other than to open an attachment in an email, though that is the most common way. Email virus infections occur when the user opens up an email with an attachment and downloads the attachment to the hard drive of the PC. What happens from there can vary greatly but in general what happens is the attachment, which is usually an EXE file, when saved, releases some code that performs an action on your computer. This can be anything from getting private information such as passwords and credit card numbers and transmitting it to the sender of the email to simply wiping out your hard drive to the point where it is beyond repair. There are debates as to which is worse.

Another way to get a virus, and this is the scarier one, is to go to a web site who's server has been infected with a virus. This virus can be passed along through the Internet connection and place a dangerous file on your hard drive. Again, the actions taken afterward by the virus can be just about anything.

So what exactly does anti virus software do about this? In simple layman's terms the anti virus software detects the intruding file and tries to do several things in this order. First it tries to delete the file before it can ever even get saved to your hard drive. If it is successful, it is as if the file never existed and no harm is done. Second, if it can't delete the file it tries to repair it, if it is a file that is actually yours to begin with and has been modified by the virus itself. If it can repair the file again it is as if nothing happened.

Third, if it can't repair the file then as a last resort it places the file in quarantine so that it can't infect any other files. Yes, viruses can spread. In this case some harm may have been done and you may have to replace the file that has been infected with a new copy. Sometimes this requires reinstalling the software the file came from. Other times the file is simply lost, especially if it is a user created file, though it may be possible to recreate the file depending on what kind of data it contained.

So how does anti virus software detect viruses? To put it simply, your anti virus software has a list of known viruses. It scans every file that you download to your PC and checks it against this list. If it finds a match it warns you of the virus giving you the name of it and then attempts to go through the steps I've outlined above.

So where does this list come from? Well, that's the hard part and the reason that anti virus software can never be 100%. The list comes from known viruses that the software company has either come in contact with itself or viruses sent to them from users who have been attacked. Therein lies the less than 100% effectiveness of anti virus software. There is always a chance that you will be the first one attacked by a new virus. You won't know it until something goes wrong with your computer and then after you report the problem to Norton or McAfee they will have you send them the file you think caused the problem and run tests on it. No, it's not an exact science but it's the best we have.

So since anti virus is not a sure fire prevention the best prevention is not to download attachments when you have no idea who sent them to you, make sure your OS has the latest patches and be very careful about what web sites you go to.

At least you don't have to drink your mother's chicken soup

About The Author: Michael Russell Your Independent guide to Anti Virus