Abstract: A notification system for a hierarchical group of consumer users of mobile devices in communication with a cellular telecommunications network is described in the application. The notification system comprises a security platform in a core of a cellular telecommunications network, and a secure consumer platform. The secure consumer platform stores: an indication of a Mobile Station International Subscriber Directory Number (MSISDN) for a subscription of each user of the group registered to the cellular telecommunications network; a hierarchical relation between the MSISDNs of one or more parent users of the group of users and the MSISDNs of one or more child users of the group of users; and a security profile for the or each child user of the group of users including an indication of an application download notification flag. The secure consumer platform is configured to signal changes in application download notification flag settings for users to the security platform keyed by MSISDN.