A method of securing media across an IP Multimedia Subsystem, IMS, network where the media transits via first and second media gateway functions of the IMS network which are controlled by respective first and second media gateway controllers acting as back-to-back Session Initiation Protocol, SIP, user agents. The method comprises sending from the first media gateway controller to the second media gateway controller, or to anode upstream of the second media gateway controller, security information of the first media gateway function, and using the sent information to secure media between the first and second media gateway functions or between the first media gateway function and said upstream node.