1. A method, comprising: obtaining, by a system comprising a processor, seed information, wherein the seed information comprises privacy profile settings of on-line social network users; comparing, by the system, the seed information to a random population of on-line social network users, resulting in a comparison; reducing, by the system, a sampling size of a total population of on-line social network users according to the comparison, resulting in a reduced sampling of on-line social network users; comparing, by the system, the reduced sampling of on-line social network users to one of a social graph, a generalized profile of on-line social network users determined from the total population of on-line social network users, or a combination thereof; determining, by the system, the social graph from a randomized-walk algorithm applied to an on-line social network of the on-line social network users; and identifying, by the system, an outlier in the reduced sampling of on-line social network users based on relationships between the on-line social network users, and based on one of ambient or publicly available information combined with an intra-graph property of the on-line social network users, wherein the outlier does not conform to one of the social graph or the generalized profile of on-line social network users, wherein the randomized-walk algorithm comprises a Metropolis-Hastings algorithm, and wherein the seed information is received from equipment of a law enforcement agency.