  The intrusiveness and the increasing invasiveness of online advertising have,
in the last few years, raised serious concerns regarding user privacy and Web
usability. As a reaction to these concerns, we have witnessed the emergence of
a myriad of ad-blocking and anti-tracking tools, whose aim is to return control
to users over advertising. The problem with these technologies, however, is
that they are extremely limited and radical in their approach: users can only
choose either to block or allow all ads. With around 200 million people
regularly using these tools, the economic model of the Web ---in which users
get content free in return for allowing advertisers to show them ads--- is at
serious peril. In this paper, we propose a smart Web technology that aims at
bringing transparency to online advertising, so that users can make an informed
and equitable decision regarding ad blocking. The proposed technology is
implemented as a Web-browser extension and enables users to exert fine-grained
control over advertising, thus providing them with certain guarantees in terms
of privacy and browsing experience, while preserving the Internet economic
model. Experimental results in a real environment demonstrate the suitability
and feasibility of our approach, and provide preliminary findings on behavioral
targeting from real user browsing profiles.
