Spybot Search and Destroy searches your hard drive for so-called spy- or adbots; that is, little modules that are responsible for the ads many programs display. Many of these modules also transmit information, including your surfing behavior on the Internet. If it finds such modules, it can remove them. In most cases the host still runs fine after removing the spyware/adware.
Another feature is the removal of usage tracks, which makes it more complicated for unknown spybots to transmit useful data. The list of last visited websites, opened files, started programs, cookies, all that and more can be cleaned. Supported are the three major browsers Internet Explorer, Netscape Communicator, and Opera.