Patent ID: 7860037

Claim:
A telecommunications system for communicating internet packets between a mobile communications user equipment forming a correspondent node and a mobile node via an external packet data communications network, the system comprising: a packet radio network operable to provide a plurality of packet data bearers for communicating the internet packets with nodes attached to the packet radio network, each of the bearers being defined with respect to a source address of the internet packets, the packet radio network including a gateway support node operable to provide an interface between the external network and the packet radio network, wherein the gateway support node is operable to detect whether an internet packet is for providing a binding update to the correspondent node of a first source address of the mobile node to a care-of-address of the mobile node, and if the internet packet is a binding update, to confirm the care of address as a legitimate destination address of the mobile node, and to allow egress of internet packets sent from the correspondent node having the care-of-address of the mobile node as the destination address from the gateway support node to the external network if the care of address is legitimate and block any internet packets sent from the correspondent node using a destination address which is not legitimate; wherein the gateway support node includes a security function operable to control the egress of the internet packets from the packet radio network by comparing the destination address of the internet packet sent from the correspondent node with a list of legitimate destination addresses stored in a data store, the security function allowing egress of the internet packet from the packet radio network if the destination address of the internet packet appears in the list, and otherwise dropping the internet packet, the care-of-address of the mobile node being added to the list upon detecting the binding update.