fraud needs a few days to be detected, SO huge amounts of money can be lost by these providers. Roaming fraud is an example that motivates the issue of collaboration between different providers. In fact, whenever a provider detects a suspicious activity from a user who has a subscription with another provider, the latter has to be informed without delay in order to compare the user current behavior to the one stored in the subscription issuing provider and also to this provider policies. A more elaborate method is to exchange users' information between providers whenever there is an agreement between them. This technique cannot be achieved, however, without addressing legal issues such as privacy and data exchange. 24.3.2 Steps Towards the Anti-Fraud Framework A major step in the process of providing any public service is to ensure the security of this service. This involves securing access to the servers and databases to avoid malicious hackers and instaling firewalls and fraud detec- tion solutions. When considering services such as e-mail, e-commerce or tra- ditional telecommunication services, there are various solutions addressing the aspect of fraud detection. A novel service such as VoIP bears great sim- ilarity to traditional telecommunication services, thus it could also utilize some of those available solutions. However, to provide a truly secure VoIP infrastructure one needs to address a broader range of scenarios that accom- modate the specific characteristics of VoIP signaling protocols as well as the open and distributed nature of VoIP. To provide effective counter measures against fraud in the SAFER framework, we will be investigating the following points and provide the appropriate solutions in the form of specifications and implementations. 1. Placement analysis: As a first step in protecting the VoIP system, a detailed look into the used signaling protocols, mainly SIP, and VoIP © 2009 by Taylor & Francis Group, LLC SIP Handbook: Services, Technologies, and Security usage scenarios will be taken