03.603GPPGeneral Packet Radio Service (GPRS)Release 1998Service descriptionStage 2TS
This screening mechanism may be performed by routers and firewalls, and performs the selection of which packets to allow and which to deny.
Only network-controlled message screening shall be supported. Network-controlled screening is used to protect the GPRS network from known security problems, and the screening provided by a certain PLMN is applied independently of the MS user. Network-controlled screening is outside the scope of GPRS standardisation.