SUMMARY
Users' awareness of the extent of information implicit in their geo-profiles on social networks is limited. This questions the validity of their consent to the collection, storage and use of their data. Tools for location privacy awareness are needed that provide users with accessible means for understanding the implicit content in their location information as well as a view of the level of risk to their privacy as a consequence of disclosing this information. Towards this goal, an abstract model of location privacy threat levels is first derived from a user study involving 186 users. This is then used to inform the design of a prototype privacy feedback tool for a location-based social network. Another user study involving 338 users of this network is carried out to test the effectiveness of the proposed design. Findings confirm the strong need of users for more transparent access to and control over their location profiles and guide the proposal of recommendations to the design of more privacy-sensitive geo-social networks.