Abstract Technology has advanced to the point that a user's use of the Web can be monitored between sessions by virtually anyone. Text files placed on a user's computer, known as cookies, can provide some companies with personal information about the user and can even track which sites the user has visited. This personal information can later be sold or exploited, putting your privacy at risk. In recent years and months, the use of the Internet, especially the World Wide Web, has grown by leaps and bounds. One aspect of web usage that has become nearly ubiquitous is web advertising, particularly banner ads. However, in recent times, data mining techniques applied to data collected through web advertising have advanced to the point of putting individual privacy at risk. The threat of personally identifiable information being linked to individuals is a clear and present danger, and various privacy organizations have filed complaints with the Federal Trade Commission regarding these issues (Federal Trade Commission). This document is an examination of privacy issues related to web advertising. Banner advertising should be examined in a different light than static advertising because banner advertising is directed at individual consumers. While static advertising, where an advertisement is hardcoded into a website, is quite common, banner advertising is much more common because it gives advertisers the opportunity to both personalize advertisements for individual users and collect data on these consumers. Web advertising has grown to such a level that it has become a $934.3 million industry (http://adres.internet.com/stories/article/0,1401,7561_231431,00.html). Furthermore, personalization has become a very serious priority for advertisers (and content producers in general) as repeat business now comprises more than half of all e-business transactions (http://adres.internet.com/stories /article/0, 1401,7561_231431,00.html). Besides customization, the other benefit of banner ads is that it allows the companies in question to practice data mining techniques that can significantly increase their revenues. “By combining the information collected by their website traffic analysis tools with other data sources, such as customer databases, online marketers can extract data about their website traffic to maximize effectiveness and return on the investment (ROI) of their websites." (Sane.com) The difference between data mining techniques and traditional data extraction techniques is that data mining "extracts information from a database of which the user does not knew existed" (Thearling), as opposed to traditional data mining, where the user is rarely surprised by the information collected. Although these