The fact is that any computer can become infected at any time despite any protection being used. There are mainly two reasons for this:
1) New forms of malicious software that have yet to be identified
2) Behavior of the user
No one antivirus software package is going to catch everything. When a new virus is created and released it may be a couple of weeks or so before antivirus software writers can create a solution to that particular threat and then release it as an update. In that period of time millions of computers can become infected despite having antivirus software installed.
And just because the update is available does not mean that the user will update his software.
Also it is important to add that a lot of people purchase antivirus software after already experiencing problems with their computers, I mean that is what motivates them to make the purchase in the first place. Well, then it is too late. It is possible that the antivirus software will not install properly. It may come under attack by the existing infection. And perhaps the user does not even know that his antivirus software is not working properly, clearing the way for other infections.
No amount of firewalls or other security software can stop a user from downloading an infected file. Happens everyday.
Or how about the user that thinks it is ok to join a file sharing network? 'Borrows' music from his friends computer? Or visits porn sites? Or tries to get cracks to software? Or downloads pretty much anything that is free on the internet? These are behaviors on the part of the user that will get him/her infected despite having antivirus.
All that being said, why use a large resourse hog of an antivirus such as McAfee or Norton when there are smaller alternatives that do the same thing, some from free?
And we haven't even touched on the fact that not all malicious software is considered a virus. The term VIRUS refers mainly to the way that particular infection is spread. But what about adware, spyware, foistware, greyware, etc, etc, etc? Antivirus software isn't going to touch these.
Edited by Albert Frankenstein, 27 August 2006 - 06:25 AM.