Abstract
With the increasing popularity of online social networks (OSNs) and the ability to access and exchange sensitive user information, user privacy concerns become an important issue which have attracted the attention of researchers and policymakers. For example, deleted pictures or pictures in deleted posts may not be deleted from the OSN server immediately, and hence accessible to another unauthorized user. In this paper, we highlight the deletion delay issue in seven popular OSNs, namely: Facebook, Instagram, MySpace, Tumblr, Flickr, Google+ and Weibo, which can be exploited by another unauthorized user to gain access to these pictures. To ensure OSN users are able to achieve a higher level of privacy, we propose a conceptual privacy-preserving tool for photo sharing, without compromising on transparency and real-time sharing features. We demonstrate the utility of the tool by prototyping a browser extension, which does not require modification of existing OSN systems.