|| Ad networks are companies that pay software developers and web sites money for allowing their ads to be shown when people use their software or visit their sites. These ads are generally in the form of popups and present you with some sort of advertisement. The problem with these networks is that they place cookies on your computer each time you open an ad served by the particular network. This allows the advertising network to track your movements across the Internet by reading the information contained in the cookies every time you connect to a site that they are on. Networks that employ this method are ones like Double Click, Value Click, Gain, and Radiate.