The better kinds of Security Software will typically log on to their manufacturer’s website at regular or specified intervals and download updates for virus and worm definitions. While the downloads can slow down your computer’s performance, perhaps even quite considerably, depending on the program and the systems involved, having updated threat definitions is absolutely vital for keeping your computer safe from the new threat being developed by unethical programmers everyday. Thus, it is important to let the security software get the new threat definitions as soon as is possible, for your own benefit.