The present disclosure provides a system and method for applying authentication and security policies in a SIP environment. In accordance with one embodiment, there is provided a method for use on a SIP server, comprising: establishing a persistent connection with a user agent (UA); initiating an idle connection timeout countdown timer; performing authentication of an initial REGISTER request using a first level of authentication; and terminating the persistent connection when the initial REGISTER request is not validated before expiry of the idle connection timeout countdown timer.