s- tigate approaches for combating fraud attempts as seen today in the telecommunications world, it will also aim at identifying other attack scenarios that target the VoIP protocol and application architecture. 2. Multi-layered adaptive fraud detection: The VoIP anti-fraud solutions to be developed within this framework will on the one side investigate the optimal approach for applying state-of-the-art algorithms to VoIP usage scenarios. On the other side, they will also investigate the use of different techniques (rule based, intelligence based) in conjunction with each other in order to provide the best detection rate. Resource effective solutions: On the one hand, the design of the SAFER detection framework and algorithms will take the specific characteristic of VoIP protocols and services into account. On the other hand, it has to accommodate the needs of the VoIP providers-often small enterprises themselves-in terms of low cost solutions and open and distributed architecture. Thereby, the design of the fraud detection algorithms has to C 2009 by Taylor & Francis Group, LLC Towards a Fraud Detection Framework in VoIP Networks target resource efficient solutions with relatively low CPU and memory consumption. 4. Impact on the service quality: The anti-fraud techniques to be imple- mented for protecting the VoIP infrastructures cannot be deployed in a real world if their impact on the service under consideration is neg- ative. The issues that can be a handicap for the developed techniques to be used are in particular, high complexity, expensive computation, high false alarm rate, and refusing transactions due to a fear of potential fraud. 5. Inter-provider collaboration: The fraud activities might go beyond one provider to another. In the case of fraud roaming, the attacker might obtain fraudulently a subscription from a provider and use it in high value activities (e.g., call selling to expensive locations, gain access to personalised services, etc) in the network of another provider. Currently, this kind of 