Cookies and the Common Law: Are Internet Advertisers Trespassing on Our Computers?

61 Pages Posted: 4 Nov 2004

See all articles by Michael R. Siebecker

Michael R. Siebecker

University of Denver Sturm College of Law


Are Internet advertisers trespassing on our computers? The question arises due to the increasing reliance upon cookie technology by Internet advertising firms as the primary means to match online ads with the specific interests and characteristics of individual Internet users.

It seems that whenever we visit a Web site, we are barraged with an increasing number of blinking banner advertisements hocking products and services of every imaginable sort. More than sixty billion advertisements per month are carefully selected for us and sent to our computers by a single Internet advertising firm, DoubleClick, Inc. In order to increase the effectiveness of the ads, DoubleClick deposits small text files or "cookies" on our computers in addition to sending us the banner advertisements. Like most other Internet advertisers, DoubleClick uses cookie files to collect and maintain detailed consumer profiles that reflect the online practices, preferences and other personal characteristics of each individual who surfs the Web. Based on those detailed consumer profiles, DoubleClick places on the pages of affiliated sites various banner advertisements of client companies that target the specific interests of individuals who happen to visit any DoubleClick affiliated site. Since its inception, DoubleClick alone has placed hundreds of billions of targeted banner advertisements for client companies on sites across the Internet and some estimate that those ads have been viewed by a majority of all Internet users.

The project here is to address in a rather comprehensive fashion the simple question of whether the use of cookie technology exposes Internet advertisers to liability on trespass to chattels grounds. In light of the current reticence of courts to interpret existing federal statutes in a manner that covers cookies, an investigation of how common law tort principles might apply to cookie technology seems especially important. In the end, the examination reveals that a very strong case supports imposing liability on DoubleClick and other Internet advertisers based on a common law theory of trespass to chattels. And while the purpose here is not to suggest that common law claims should supplant statutory causes of action, framing a claim based on common law trespass to chattels principles could provide certain strategic advantages that a statutory framework might not afford.

Keywords: Internet, Computers, Trespass, Advertising, Technology, Common Law, Privacy, Cookies

Suggested Citation

Siebecker, Michael R., Cookies and the Common Law: Are Internet Advertisers Trespassing on Our Computers?. Southern California Law Review, Vol. 76, No. 4, p. 893, May 2003. Available at SSRN:

Michael R. Siebecker (Contact Author)

University of Denver Sturm College of Law ( email )

2255 E. Evans Avenue
Denver, CO 80208
United States
303-871-6057 (Phone)

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