Internet sales are growing very fast, thus becoming a major target for fraudsters. This fraud is mostly perpetrated by international organized crime rings. Fighting fraud is thus critical for our societies' security. Classically, fraud detection has been implemented through data mining techniques; however, social networks techniques have recently emerged in the security domain. We present here a methodology to use social networks together with data mining for fraud analysis and illustrate the approach through results recently obtained in an ongoing project, with transaction data provided by a major national network.