MYDOOM is a Windows email-propagating worm used as one component of the July 2009 attacks against U.S. and South Korean websites. In the documented chain, a Dozer dropper installed W32.Mydoom.A, which in turn dropped a Mytob component that harvested email addresses and mailed the dropper onward. A related MYDOOM variant downloaded a distributed-denial-of-service component and later a destructive payload designed to damage infected hard drives after a set date, combining propagation, attack, and destructive effects.