ABSTRACTAuthentication, authorization, and accounting services provide the framework on top of which a reliable, secure, and robust accounting system can be built. In a previous work of ours, we have presented a flexible and, most importantly, generic accounting scheme for next generation networks. In this paper, we substantially improve our previous work by providing the required Diameter application namely SIP‐Accounting (SIPA) that enables the use of our accounting scheme for Session Initiation Protocol (SIP) services. Additionally, in an effort to protect the service providers and the end users against accounting frauds, we implement an add‐on mechanism referred to as SIPA+ to combat attacks targeting the core accounting functions and the integrity of the respective accounting messages. Using the implemented SIPA and SIPA+ prototypes, we conducted a complete set of experiments testing several configurations and two distinct scenarios. The results reveal that the proposed accounting system and its security add‐on are fully operable in SIP environments without incurring much cost in terms of performance and overhead. Copyright © 2011 John Wiley & Sons, Ltd.