Mitigating Adverse Effects of Using Online Social Networks

Online Social Networks (OSNs), such as Facebook and Google+, are network-based communication systems. They allow their users to create persistent digital representations of themselves, called user profiles, and to establish explicit connections to other user profiles within a bounded system. OSNs have become popular services that attract more than one billion users. The ubiquity of mobile devices, which support accessing OSNs from anywhere, causes OSNs to be powerful communication tools that change the way how people interact with each other. OSNs gain importance for the daily life of their users by becoming an access channel to parts of their social environment. However, using OSNs puts users at the risk of various undesired side-effects, such as cyber bullying, being forced to grant content use licenses to OSN providers, facilitating social engineering attacks, losing the job due to improper public comments and even imprisoning in autocratic countries. In addition, users of OSNs are subject to crowd engineering. These side-effects are caused by both: sharing data with too many or the wrong recipients and implications of the fact that OSNs are operated by commercial companies. This thesis contributes to understand the origin of these side-effects and approaches to mitigate the latter without limiting the power of the OSN. We elaborate user behavior in the most popular OSN, Facebook, and introduce a color-based interface that simplifies audience selection in OSNs. Furthermore, we improve decentralized OSNs (DOSNs) that are not operated by commercial OSN providers to avoid ownership implications. Our first step is to gain understanding of the sources of adverse effects by evaluating OSN usage in detail. We answer the questions: How intensive do users use the most popular OSN, Facebook? How do users orchestrate the variety of communication functions? With whom do users communicate? On the way to understand causes of side-effects, a second step is to investigate the content sharing preferences amongst users from various countries. Since users are unable to choose their audience properly, evaluating the actual settings is insufficient. To circumvent this issue, we developed a browser plug-in that simplifies the audience selection. Decentralizing OSNs is a way to avoid implications of commercial companies being the owner and operator of the OSNs. In spite of their potential to avoid adverse effects, DOSNs are not widely adopted. They suffer from the lack of performance and functionality, compared with their popular counterparts. We contribute to mitigate the lack by surveying the state-of-the-art in the field of DOSNs, introducing a search mechanism that allows to find user handles without leaking sensible information, allowing P2P-based DOSNs to be operated under high churn and by prefetching videos based on locally-available information