features of VoIP User, it also has a web forum with RSS feeds and a telecom-focused news feed. There are many discussion forums on topics including VoIP, telephony, messaging, presence, open source and Web 2.0. The forum is visited by a large international community, including many industry innovators and telecom experts. Staff and founders VoIP User was created by Dean Elwood and Tjardick van der Kraan in July 2003 and both are still intimately involved in the running of both network and web site. Both Dean and Tjardick are internationally known figures in the telecom and Web 2.0 world, and both are huge fans of gadgets and technology. A small team of volunteers administer the forums and help maintain the VoIP network and imagining and creating new features for VoIP User. The forum community itself also contributes a lot to VoIP User, with many experienced developers, gurus and engineers offering help and advice to others with questions and problems. Fraud As with any Telco that enables calls to be connected internationally, the problem of fraud does sometimes arise. Companies and individuals wanting to make a “quick buck” have sometimes tried to harness the VoIP User network in order to connect paying customers with what is, essentially, a free service, allowing margin to be skimmed off for the fraudster. VoIP User handles this with a variety of measures, including the 10-minute call limit, and in extremis blocking of traffic to specific high fraud risk destinations altogether. Over the years VoIP User has seen many patterns of call fraud and has created tools and techniques to combat them based on the detection of those patterns. Technology, protocols and architecture VoIP User currently supports Session Initiation Protocol (SIP) for both incoming and outgoing calls and IAX2 protocol for incoming calls. It also supports SIP SIMPLE for Instant Messaging and Presence. Most of the VoIP User core network is constructed using industry-standard PC servers, running Linux and telephony applications that include Asterisk (for audio messaging media and echotesting services), OpenSER (for SIP proxy and registrar duties) and edge controllers and media gateways being a combination of open-source and custom written software. Call rating, CDR collection and account handling software is custom written and based on FreeRADIUS and the integration of RADIUS messaging to the media gateways and SIP B2BUAs residing at the network edge. VoIP User currently operates 9 servers hosted globally and with