Date Added: May 2009
Current Voice over IP (VoIP) services are regarded less secure than the traditional Public Switched Telephone Network (PSTN). This is due to the fact that VoIP services are frequently deployed in an relatively open environment, so that VoIP infrastructures can be easily accessed by potential attackers. Furthermore, current VoIP services heavily rely on other public Internet infrastructures shared with other applications. Thus, the vulnerabilities of these Internet infrastructures can affect VoIP applications as well. Nevertheless, deployed in a closed environment with independent protocols, PSTN has never faced similar risks. The main goal of this licentiate paper is the discussion of security issues of the Session Initiation Protocol (SIP), which serves as a signalling protocol for VoIP services.