Modern telecommunications networks, particularly mobile networks provide the potential for fraudsters to make use of telecommunication services (Voice, Data, Fax etc.) without the intent to pay. A number of different scenarios are exploited and it is up to the network operator or service provider to detect misuse where it occurs and to stop it at the earliest possible opportunity.
The scale of frauds can be many thousand of ECU per day on a single account when International or Premium rate numbers are called. The most common types of fraud that effect networks like GSM are related to the ability to sell calls at below market price using stolen air-time/equipment where the user of the equipment does not intend to pay the network operator or service provider. Fraudulent subscribers often avoid payment by obtaining a handset and a subscription to a GSM network by fraudulently giving details and justifications to the network operators/service provider. If there are not good controls within the network the subscriber can make a large volume of calls to expensive destinations and accumulate a large bill.
Roaming, in co-ordination with advanced services such as call transfer and multi-party calls, complicates the issue further, requiring control of the customer within the VPLMN. Many simultaneous calls can be set up and large bills accumulated in a short time. At present no system exists within the GSM network architecture for speedily transferring information on subscriber activity from the VPLMN to the HPLMN.
In the future, SIMs may roam to non-GSM networks, further broadening the area over which control is required. It is recognised that if FIGS is implemented in non-GSM networks that suitable inter-working units will be required to translate commands and information.
The PLMN network should be able to supply relevant information to the HPLMN network so it can make a decision on whether to terminate a call or to change the Operator Determined Barring (ODB) configuration for the specific subscriber. This decision will be carried out by the HPLMN or service provider. It is recognised that there is a limit to the type and volume of information that can be transferred between the VPLMN and the HPLMN. Therefore the requirement for the system is that distilled and standardised information must be supplied between the VPLMN and HPLMN.
The following minimum capabilities are required. See Figure 1
Within the Home Network:
Within the VPLMN:
to mark a subscriber, defined by the IMSI or MSISDN, as being under FIGS control ("FIG Set");
to receive from the VPLMN the data described below;
to remove the monitoring of a subscriber's activities ("FIGS Unset").
to transmit to the HPLMN information (FIGS Data):
at the start of a call;
at the end of a call;
during a call` for long calls or at the mid-call invocation of supplementary services.
The following service conditions shall apply:
FIGS shall not modify the VPLMN's service;
FIGS should not alter any standard GSM functionality seen by the customer or effect the service quality;
If the VPLMN network does not have the resources to support a FIGS Set command it shall respond accordingly to the HPLMN.
The need for up to date information is a critical part of any fraud information system. The sooner data is transferred to the HPLMN, the sooner fraud can be stopped. Therefore the proscribed information shall be transferred from the VPLMN to the HPLMN within two minutes of the occurrence of a FIGS-monitored event
The information shall preferably be transferred from the VPLMN to the HPLMN over existing communication links (e.g. SS7 signalling links).
If the support of FIGS is causing overload within the VPLMN the FIGS system shall not permit the marking of new subscribers. The VPLMN should therefore handle up to a realistic limit any requests for marking of subscribers and be able to support the associated data transfer. The setting of this limit is outside the scope of this report.
Each VPLMN should limit the number of subscribers that each HPLMN may request to be monitored using FIGS. Otherwise an HPLMN may take more than its "fair share"
of the FIGS processing capability of a VPLMN.
A mechanism shall be required whereby a VPLMN can charge an HPLMN for the bulk data transfer made to that HPLMN.