This authoritative and practical book offers a current and comprehensive understanding of VoIP (Voice over IP) security. You learn how to design and implement secure VoIP networks and services, and how to integrate VoIP securely in existing data networks. You discover how emerging IETF SIP and media security standards will affect future VoIP deployment, and how end-to-end encryption may be deployed to eventually protect all VoIP calls. The book explains Internet security basics, attack types and methods, and details all the key security aspects of a data and VoIP systems and networks, including identity, authentication, signaling, and media encryption. This practical resource discusses security architectures of perimeter vs. end-to-end security in terms of VoIP systems. You also find security approaches and architectures in related applications, such as the World Wide Web, Secure Shell, and the PSTN. A chapter on client and server security discusses general security of Internet hosts in a VoIP system. What's more, the book presents current techniques to combat spam and covers the future problems of spim (spam over instant messaging) and spit (spam over internet telephony).