The problem of online privacy is often reduced to individual decisions to hide or reveal personal information in online social networks (OSNs). However, with the increasing use of OSNs, it becomes more important to understand the role of the social network in disclosing personal information that a user has not revealed voluntarily: How much of our private information do our friends disclose about us, and how much of our privacy is lost simply because of online social interaction? Without strong technical effort, an OSN may be able to exploit the assortativity of human private features, this way constructing shadow profiles with information that users chose not to share. Furthermore, because many users share their phone and email contact lists, this allows an OSN to create full shadow profiles for people who do not even have an account for this OSN. We empirically test the feasibility of constructing shadow profiles of sexual orientation for users and non-users, using data from more than 3 Million accounts of a single OSN. We quantify a lower bound for the predictive power derived from the social network of a user, to demonstrate how the predictability of sexual orientation increases with the size of this network and the tendency to share personal information. This allows us to define a privacy leak factor that links individual privacy loss with the decision of other individuals to disclose information. Our statistical analysis reveals that some individuals are at a higher risk of privacy loss, as prediction accuracy increases for users with a larger and more homogeneous first- and second-order neighborhood of their social network. While we do not provide evidence that shadow profiles exist at all, our results show that disclosing of private information is not restricted to an individual choice, but becomes a collective decision that has implications for policy and privacy regulation.
In this article, we evaluate the accuracy of partial and full shadow profiles for the sexual orientation of users and non-users of the Friendster social network. Our analysis builds on the sequence of users joining Friendster to evaluate predictions over individuals without a user account in a similar manner as done in @cite_31 where the links between non-users are inferred. Knowing in which sequence the users joined Friendster has freed us from having to utilize a network growth model in our analysis. Furthermore, we pay special attention to the ratios of friends belonging to each orientation in the neighborhood of users at a given time in the growth of the network. Our results should be compared with previous work on sexual orientation of users in smaller datasets @cite_28 . To our knowledge, our work is the first to address the possibility of creating full shadow profiles for the sexual orientation of non-users from a large scale OSN.
@cite_28 @cite_31
2085427378 2037900945
Public information about one's coworkers, friends, family, and acquaintances, as well as one's associations with them, implicitly reveals private information. Social-networking websites, e-mail, instant messaging, telephone, and VoIP are all technologies steeped in network data—data relating one person to another. Network data shifts the locus of information control away from individuals, as the individual's traditional and absolute discretion is replaced by that of his social-network. Our research demonstrates a method for accurately predicting the sexual orientation of Facebook users by analyzing friendship associations. After analyzing 4,080 Facebook profiles from the MIT network, we determined that the percentage of a given user's friends who self-identify as gay male is strongly correlated with the sexual orientation of that user, and we developed a logistic regression classifier with strong predictive power. Although we studied Facebook friendship ties, network data is pervasive in the broader context of computer-mediated communication, raising significant privacy issues for communication technologies to which there are no neat solutions. Members of social network platforms often choose to reveal private information, and thus sacrifice some of their privacy, in exchange for the manifold opportunities and amenities offered by such platforms. In this article, we show that the seemingly innocuous combination of knowledge of confirmed contacts between members on the one hand and their email contacts to non-members on the other hand provides enough information to deduce a substantial proportion of relationships between non-members. Using machine learning we achieve an area under the (receiver operating characteristic) curve () of at least for predicting whether two non-members known by the same member are connected or not, even for conservative estimates of the overall proportion of members, and the proportion of members disclosing their contacts.