Abstract: An improved system for detecting and preventing telecommunications fraud prior to call connection, in which attempted calls are screened for fraud at the point of calling card validation in the SCP. The SCP accesses a database holding a variety of fraud decision nodes that may be interrelated and grouped together to cooperatively define fraud screening trees against which attempted calls may be tested. A fraud screening tree ultimately produces a fraud prediction based on a variety of information concerning the attempted call. The present invention therefore facilitates fraud screening with greater granularity and customization.