1. A method, comprising: obtaining seed information; reducing a sampling size of a total population of on-line social network (OSN) users according to the seed information using a processor; comparing the reduced sampling of OSN users to at least one of a social graph or a generalized profile of OSN users determined from the total population of OSN users, the comparison being performed by the processor; and identifying one or more outliers in the reduced sampling of OSN users that do not conform to the social graph or the generalized profile of OSN users.