Modeling Exposure in Online Social Networks

In online social networks (OSNs), the privacy of users is impacted by exposure of information about those users to other users of the system. Various factors, including design and user behavior, may affect the degree to which information about users is exposed. We propose the notion of knowledge exposure that measures the probability that information about users will be seen by others. We argue that such a measure can give OSN users and designers insight about how privacy is affected based on system design and user behavior. We present exposure as a promising notion that can complement privacy control efforts in an OSN rather than replacing existing measures such as access control. We provide a formal model of exposure in an OSN, and demonstrate through experiments how it can be calculated for various information items.