There are several ways that computers become infected with SpyWare we will only discuss the two most common ways. The most common way SpyWare is added to a computer is by shareware authors. Shareware is programs that are designed and provided to the public at no charge. Most of the authors of these software packages make a profit by bundling a second program with the original. Most people do not realize this second program is being installed and this second program cannot usually be removed without the removal of the original program. This second program is designed to gather information about the user, display popups, change homepages and report information gathered about the user back to the programmer. The authors are then paid by the number advertisements that are displayed and the authors also sell the information gathered about users to marketing companies. A good example of this type of program is peer to peer file sharing software.

One can also become infected simply by visiting a website. While this does not happen as frequently as people believe, it does happen. The only way this is possible on a windows machine is if certain user options are selected. This way of being infected is nearly impossible to protect against without the help of a SpyWare program such as Ad Aware and SpyBot S&D.