1. A method performed by a mobile network, the method comprising the steps performed by one or more network elements of: detecting a signal from a network element indicating that a subscriber wishes to become active on the network using a mobile device; generating a signature derived from a device identifier and a subscriber identifier, the signature not having a semantic meaning; checking if the signature is in a signature store; and if not, determining that the device/subscriber combination does not exist in the network, and storing the signature in the database; if so, determining that the device/subscriber combination already exists in the network; transmitting a notification of device/subscriber status to an external system.