The word virus has become a generic term describing a number of different types of attacks on computers using malicious code. Just about everybody has heard of computer viruses, worms, Trojan horses, and other malicious software. Many have been infected at least once, either by one of the famous attacks such as Melissa, ExploreZip, MiniZip, Code Red, NIMDA, BubbleBoy, I LoveYou, NewLove, KillerResume, Kournikova, NakedWife, or Klez; or perhaps by a lowly pest picked up in an email or through visiting some web site. A virus or worm could even be active in your machine right now, lying dormant until some trigger activates it. And in today's world, the line is blurred between viruses and marketing tools, such as pop-ups, adware, or spyware, each of which uses a certain amount of the computer's resources to display or gather data about the user.