All of them check new files on your computer against databases full of known viruses. But with new viruses being released at a rate of six per day, according to IBM simply installing virus software doesn't protect you. Users must constantly update their software by downloading the latest database of known viruses. But for even the most vigilant, conscientious virus software administrator, there's a math problem. New viruses can spread around the Internet almost instantly.
Worms can cover the globe in a matter of hours.
Under the best of circumstances, your virus software won't be updated for about 48 hours. That gives a virus a heck of a head start. There's no way any anti-virus company can keep up with that. But they're trying Since virus software tends to be reactive, virus writers currently have the upper hand in the game of cat and mouse. But plenty of efforts are under way to close the gap between safecracker and locksmith.