zalis. 2007. SIP vulnerabilities and antispit mechanisms assessment. In Proceedings of the 16th IEEE International Conference on Computer Communica- tions and Networks (ICCCN '07). Hawaii: IEEE Press. [16] SIPp. 2007. http://sipp.sourceforge.net, March. [17] Niccolini, S. 2006. SPIT prevention: State of the Art and Research Chal- lenges. Germany: Network Laboratories, NEC Europe. [18] Peterson, J. and C. Jennings. 2006. Enhancements for authenticated identity management in the session initiation protocol. RFC 4474. [19] Community efforts in the email case. 2007. http://www.stayinvisible. com/index.pl/proxy_list, March. [20] The SPIDER project. 2007. http://www.projectspider.org. Deliverable 2.2 (Spit detection and handling strategies for VoIP infrastructures). September. C 2009 by Taylor & Francis Group, LLC Towards a Fraud Detection Framework in VoIP Networks Yacine Rebahi Fraunhofer Institute for Open Communication Systems Thomas Magedanz Technical University of Berlin Dorgham Sisalem Tekelec CONTENTS 24.1 Introduction 24.2 Background 24.3 The Fraud Detection Framework Specification 24.4 Conclusion Acknowledgment References 24.1 Introduction The openness and low cost structure of Voice over IP (VoIP) services has helped Application Service Providers to attract large numbers of subscribers over the last few years. However, as evidenced by various press reports the same reasons have unfortunately also attracted attackers and malicious users. Thus, misuse of services and fraud are currently considered as one of the biggest obstacles to VoIP providers. Fraud detection has been an active area of research and development in the banking and credit card industry. In the VoIP area, there is still hardly any research or products that can assist providers in detecting anomalous behavior. Hence, providers refer to general monitoring tools and manual search methods for identifying fraud attempts. To fill this gap, we suggest a complete solution for automatic fraud detection that alarms providers when suspicious behavior is 