Despite the whimsical name, cookies are a powerful tracking tool for advertisers. They are designed to store small pieces of information on a computer to make it easier for websites to remember the computer user. In its most innocuous form the cookie is a useful item. Cookies are used to save passwords and user ID information, which is useful for people who visit websites of organizations they belong to. Thanks to cookies, the computer can “remember” this information instead of forcing the user to type it in each time he or she visits a site.

Cookies can also be used, however, to gather more personal information about users, including what they purchase, how much time they spend at different sites, what they click on, and what they purchase. Often, banner ads include cookies, so anyone who clicks on a banner ad gets a cookie placed on his or her computer. That may be fine if the cookie only tracks the user’s visits to that particular ad. Unfortunately, many banner ad companies actually collect data from cookies for all their member companies. This is how clicking on one particular ad can generate junk email, phone calls, or print mail.