A reverse proxy for VoIP : Or how to improve security in a ToIP network

Sammanfattning: The need for security is crucial in Telephony over IP (ToIP). Secure protocols have been designed as well as specific devices to fulfill that need. This master thesis examines one of such devices called Session Border Controller (SBC), which can be compared to reverse proxies for ToIP. The idea is to apply message filters to increase security. This thesis presents the reasons of SBC existence, based on the security weaknesse sa ToIP network can show. These reasons are then used to establish a list of features which can be expected from a SBC and discuss its ideal placement in a ToIP network architecture. A test methodology for SBCs is established and used on the free software Kamailio as an illustration. Following this test, improvements of this software, regarding threats prevention and attacks detection, are presented and implemented.