Spyware has quickly evolved from an online nuisance to one of the most dire threats facing the Internet. As users struggle to maintain control over their computers, many find themselves trapped in a cyclical battle against programs that install themselves without warning, open dangerous security holes and reinstall themselves after they've been deleted. The worst of these programs allow online criminals to hijack users' sensitive personal information at will. Even the most benign variants can slow computers to a crawl by wasting their processing power to provide unwanted "services." Compounding the problem are the sophisticated ploys spyware developers use to install their programs on unsuspecting users' computers. Spyware distributors often rely on security holes, clever cons, opaque "bundling" arrangements and other unsavory practices to spread their unwanted payload. As the threat has grown, so has the need to mount a coordinated defense against these unwanted programs and their adverse effects.