How do you prevent a computer virus?

The last couple of months have seen a large rise in the number of computer viruses that are out there and spreading via e-mail. The following guidelines may give you a fighting chance.

I have divided this page into two sections - a quick guide for those who are experienced, or are short on time, and a more detailed section for anyone wanting more details.

Please do not ignore computer viruses - they can range from nuisance or joke programs to ones that erase the entire hard disk.

Quick Guide:

  1. Keep a regular backup of your important files (on floppy, zip disk, writeable CD, tape, another hard disk, etc.)
  2. Be aware that most current viruses arrive as e-mail attachments. Be very suspicious of any attachment that has any of the following file extensions:

.exe .vbs .scr .vbe .com .bat .shs .cpl .dll .ocx .pif .drv .lnk .bin .sys .eml .nws (do not click on attachment files whose names end with any of the above) These attachments almost always arrive from someone you know (without that person's knowledge), so attachments are not safe just because you know the sender. Note: Opening the mail itself is safe, but clicking on any attachment can spread the virus instantly.

You should update your definition files about once a month.

  • What is a Computer Virus: A Computer Virus is simply a computer program with malicious intent. These programs are usually small in size, and the more clever ones hide themselves within other innocent programs (e.g. within NOTEPAD), hence the "virus" in their name. In fact the technical difference between a Computer Virus and a Computer Worm is that the virus inserts itself within some other legitimate program, while the Worm exists as a standalone program. From a user's perspective this distinction is somewhat moot, and a worm or a virus can do equal damage. In fact the word "worm" is used less these days, and virus is often applied to both types of programs.

Viruses are usually written by students with time on their hands, though a few are very sophisticated and obviously written by professionals (disgruntled employees, frustrated programmers etc.). While there are over 30,000 known computer viruses, the number of truly original viruses is actually quite limited, as seen by the number of copy-cat viruses that proliferate after any well-publicized virus incident. For example, there are apparently several hundred variants of the "ILoveYou" virus out there. Most are just plain copies, or minor variations of the original.