Privacy in Evolving Social Networks

Over the past decade, the use of the social networks like Facebook and Twitter, just to mention two of the most popular ones, has increased at the point of becoming ubiquitous. Many people access Social Networks Services (SNSs) on a daily basis; e.g. to read the news, share pictures with their friends or check upcoming events. Nearly 70% of the Internet users are active on SNSs, as shown by a recent survey [4]. Empirical studies have also shown that the current privacy protections offered by SNSs are very far from the users’ expectations [6, 5]. One of their weaknesses is the inability for users to express desirable privacy policies. This is because, the privacy settings offered by SNSs are too coarse-grained. Furthermore, many users are not fully aware of the result of activating a privacy policy or if the policy protects their personal data as they expect. We believe citizens should be in power to control and decide on how much information to make public. One way to do so is by providing users with means to define their own privacy policies and give guarantees that they will be respected. Privacy in SNSs may be compromised in different ways: from direct observation of what is posted (seen by non-allowed agents), by inferring properties of data (metadata privacy leakages), indirectly from the topology of the SN (e.g., knowing who our friends are), to more elaborate intentional attackers such as sniffers or harvesters [3]. Among others, one of the origins of these attacks comes from their privacy enforcement mechanism, the so called Relationship-Based Access Control (ReBAC) [2]. We aim at developing a privacy enforcement mechanism which offers social network users the possibility of expressing finer-grained privacy policies, enabling them to deal with (certain kinds of) implicit disclosure of sensitive information. Moreover this mechanism should take into account that the social network evolves and enforce the privacy policies as events occur. We have developed the privacy policy framework FPPF for social networks [8, 7], which is briefly described in next section.