We have all become users of free Internet sites. Google, Yahoo, and Facebook provide convenient resources, such as email and search tools. Millions of people use these sites every day. How is it possible that online companies benefit by supplying services s for free? The answer is that although we assume that are customers of sell to Google or Facebook, in fact we are not. We are the product that these companies their real customers: advertisers. Every we look for information on Google or click on a Facebook link, we are time being watched. Every time we send email, the content of our mail is being examined Information about what we are interested in, what products we like, or what books or Academy Award movies we are interested in is collected by these online companies.