Privacy Policy Inference of User-Uploaded Images on Content Sharing Sites

With the increasing volume of images users share through social sites, maintaining privacy has become a major problem, as demonstrated by a recent wave of publicized incidents where users inadvertently shared personal information. In light of these incidents, the need of tools to help users control access to their shared content is apparent. Toward addressing this need, we propose an Adaptive Privacy Policy Prediction (A3P) system to help users compose privacy settings for their images. We examine the role of social context, image content, and metadata as possible indicators of users’ privacy preferences. We propose a two-level framework which according to the user’s available history on the site, determines the best available privacy policy for the user’s images being uploaded. Our solution relies on an image classification framework for image categories which may be associated with similar policies, and on a policy prediction algorithm to automatically generate a policy for each newly uploaded image, also according to users’ social features. Over time, the generated policies will follow the evolution of users’ privacy attitude. We provide the results of our extensive evaluation over 5,000 policies, which demonstrate the effectiveness of our system, with prediction accuracies over 90 percent.

1 Introduction

Images are now one of the key enablers of users’ connectivity. Sharing takes place both among previously established groups of known people or social circles (e.g., Google+, Flickr or Picasa), and also increasingly with people outside the users social circles, for purposes of social discovery-to help them identify new peers and learn about peers interests and social surroundings. However, semantically rich images may reveal content-sensitive information []. Consider a photo of a students 2012 graduationceremony, for example. It could be shared within a Google+ circle or Flickr group, but may unnecessarily expose the studentsBApos familymembers and other friends. Sharing images within online content sharing sites,therefore,may quickly leadto unwanted disclosure and privacy violations [3], [24]. Further, the persistent nature of online media makes it possible for other users to collect rich aggregated information about the owner of the published content and the subjects in the published content [3], [20], [24]. The aggregated information can result in unexpected exposure of one’s social environment and lead to abuse of one’s personal information.