So now we've come to today's most common means of virus infection--via email attachments.

The letters, numbers and symbols that you read in your email do not contaminate your PC by themselves. Email contamination always involves an attachment to your email. Just like back in the days when you or your grandmother would send family photos along with a letter through the post office, those family photos that she now sends through email attachments could possibly be where virus infection of a computer begins.

The pictures that come in .jpg or .gif format will not infect your computer. The attachment has to be an executable program in order for it to be a virus threat. But today's virus Coders are so sly they can actually trick you into thinking that the .jpg or .gif file are actually just those but in reality they are executable files.

Back in the days it was rather easy to tell. The file would have an extension of either .EXE, .COM, or .BAT. Nowadays, aside from the three extensions we've mentioned, there can be a variety of extensions that could be virus threats--.VBS, .SCR, .PIF, .XLS, .DOC etc. The worse part is that as viruses become more sophisticated, the virus authors are able to actually hide the offending extension.

As we mentioned above, an innocent looking .jpg (picture) file may not actually be what it seems. It could be actually be a virus in disguise. How they do it is they put long spaces between the last letter of the "decoy" extension and the actual extension which could be any of ones we mentioned above. Here's an example: "picture.jpg                                 .scr".

The spaces are very likely much longer than the one illustrated above. Why do they do this? The answer is simple--the attachment box in your email program is only so long in length and therefore you only see the first part of the file name as the attachment. The spaces that separate the actual extension are out of view. So you are tricked into believing that the file attached is an innocuous "picture.jpg". Yes, wicked.

Now before you decide to sever a long-time friendship just because your friend has sent you hundreds of attachments via email recently, remember that a computer user is not always aware that they are sending out virus infected attachments. As mentioned earlier, viruses these days are so sophisticated they can actually attach themselves to an email without the user knowing it and send themselves out to several recipients. This is the concept of the worm at work.

Your PC becomes contaminated with a worm, the worm then starts to replicate itself by attaching itself to other programs on your PC which, when run, will allow the worm to propagate itself. Think back a few years when the most popular worm of them all, the "Iloveyou" worm (incorrectly referred to as a virus back then), actually locked down the operations of several networks worldwide.