stem we are intending to implement will not take preventive measures by itself. This would require deep involvement in the signaling process and access to the operator's user database. As our system will be designed to act as an independent component in the VoIP network, realizing such interaction is not planned. However, an open interface will be provided through which the operator can access the alarms generated by the system and use its established infrastructure for taking the preventive measures. Interface components: This part provides the necessary interface to enable the communication of SAFER with other systems as well as pro- viding the operator with various status information and configuration possibilities. - Provider and user policies: The work on placement and detec- tion analysis will result in the specification of certain detection mechanisms that can be utilized by the fraud detection system. One problematic issue with fraud is, however, that there is no simple classification. While one operator might allow for certain behavior others might consider it as a fraud attempt. Therefore, the VoIP providers deploying a fraud detection system must also have the ability to specify certain rules and policies describing which requests and usage scenarios should be prevented as well as the actions to invoke after detecting certain irregularities. These C 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security policies will enhance the detection mechanisms and ensure that the users' wishes are taken into account. Configuration interface: It is obvious from the state-of-the-art discussion, that not all detection and prevention mechanisms will be useful in each scenario. Thus, the fraud detection system will be configurable with different detection modules. Hence, to achieve a high detection rate and rapidly adjust to new fraud methods and scenarios, the SAFER system will provide for rich configuration possibilities enabling the operators to chose the appropriate detec- tion sche