A method for facilitating surveillance of a targeted user participating in communication sessions conducted over a communications network, such as a voice over Internet protocol (VoIP) network, that employs a session initiation protocol (SIP). The method includes receiving a subscription request from a third party subscriber, the subscription request identifying a targeted user to be monitored, monitoring communication sessions in which the targeted user is a participant, to detect SIP events corresponding to state transitions associated with the communication sessions. A system for facilitating surveillance of a targeted user includes an application programming interface (API) operable to receive a subscription request from a third party subscriber, the subscription request identifying the targeted user, wherein the third party subscriber is not a participant in the one or more communication sessions, and a SIP events monitoring module operable to detect one or more predetermined SIP events associated with t
