Erratum to: Web-traveler policies for images on social networks (World Wide Web,(10.1007/s11280-009-0070-8)

Images are one of the most popular types of contents shared on these sites. Most ofthese networks offer some rudimentary forms of access controls such as allowing the users tochoose who can view their profiles or the images uploaded by them. These controls howeverapply only in the perimeter of the users direct control such as desktops, profiles etc. Usershave no control over their content once it is downloaded by others. In order to enable a user totruly maintain control over his content, new access control mechanismsmust be designed so asto enable users to control their content even when managed by others. Towards fulfilling thisgap, in this paper we propose the concept of "web-traveler policies". Web-traveler policiesallow the user to specify who can view, upload or download a given image within a socialnetwork. The unique, innovative feature of web-traveler policies is that they travel with theimage, as long as it is hosted on the given social networking site. Additionally, we explore thepossibility of extending these controls across different sites, by using the concept of mashups.In the paper we prove the feasibility of this approach, by implementing a working prototype ofour approach on a real open source social network platform. We test the performance andscalability of such architecture under heavy user loads and also its resilience towards naïve attacks. This work is a first innovative step toward scalable systems for providing each userwith a centralized system for his/her own content's protection all over the web.