When a request to connected a requesting user to a target user is received by the social networking system, information associated with the requesting user and with users connected to the target user is retrieved. A fraud probability score indicating a probability that the requesting user is impersonating a user connected to the target user is determined based on the information associated with the requesting user and with users connected to the target user. Based on the fraud probability score, a determination is made whether the requesting user is a suspected imposter and remedial action is taken if imposter is suspected.