1. A method comprising: receiving a report from a reporting user of a social networking system, the report identifying an alleged imposter account in the social networking system; calculating a first fraud probability measure based on social data, the first fraud probability measure comprising a measure of the probability that the alleged imposter account is fraudulent; calculating a second fraud probability measure based on social data, the second fraud probability measure comprising a measure of the probability that an alleged authentic account is fraudulent; comparing, by a processor, the first fraud probability measure to the second fraud probability measure; and responsive to the first fraud probability measure being greater than the second fraud probability measure and greater than a minimum fraud probability threshold value, enrolling the alleged imposter account in an account verification process.