The cookie is a well-known mechanism for storing information about an Internet user on their own computer. However, the existence of cookies and their use is generally not concealed from users, who can also disallow access to cookie information. Nevertheless, to the extent that a Web site stores information about you in a cookie that you don't know about, the cookie mechanism could be considered a form of spyware. DoubleClick, a leading banner ad serving company, changed its plans to combine cookie information with database information from other sources to target ad campaigns directly to individuals without their permission. DoubleClick's current policy is not to collect "personally-identifiable" information about a user without their explicit permission or "opt-in."