Millions of ads are shown to Internet users daily, targeted to user profile. We call the function that determines who is shown what ad as the Adscape.  We perform the first large scale study of the Adscape.  We design and implement profile based crawling that enables each crawler instance to interact with the ad ecosystem as though it was a unique user with specific characteristics. We find that while targeting is widely used, there remain many instances in which delivered ads do not depend on user profile; further, ads vary more over user profiles than over websites.

It is joint work with
Paul Barford, Igor Canadi, Qiang Ma and S. Muthukrishnan