No restrictions on the type of charging model

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No restrictions on the type of charging model: Compared with fully compliant IMS security solution, the GIBA solution should not impose any restrictions on the type of charging model that can be adopted. 3GPP 3GPP TS 33.203 V12.67.0 (2014-0609) 106 Release 12
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Impact on interfaces: Interfaces that are impacted by the GIBA solution should be adequately documented to ensure interoperability between vendors. Support access over 3GPP PS domain: It is a requirement to support secure access over the 3GPP GPRS/UMTS access. Low impact on provisioning: The impact on provisioning should be low compared with the fully compliant IMS security solution. T.3 Threat Scenarios T.3.0 General To understand what controls are needed to address the security requirements, it is useful to describe some of the threat scenarios. NOTE: There are many other threats, which are outside the scope of this Annex. T.3.1 Impersonation on IMS level using the identity of an innocent user The scenario proceeds as follows: - Attacker A attaches to GPRS, GGSN allocates IP address, IPA - Attacker A registers in the IMS using his IMS identity, IDA - Attacker A sends SIP invite using his own source IP address (IPA) but with the IMS identity of B (IDB). If the binding between the IP address on the bearer level, and the public and private user identities is not checked then the attacker will succeed, i.e. A pays for IP connectivity but IMS service is fraudulently charged to B. The fraud situation is made worse if IP flow based charging is used to 'zero rate' the IP connectivity. The major problem is however that without this binding multiple users within a group "of friends" could sequentially (or possibly simultaneously) share B's private/public user identities, and thus all get (say) the push-to-talk service by just one of the group paying a monthly subscription. Without protection against this attack, operators could be restricted to IP connectivity based tariffs and, in particular, would be unable to offer bundled tariffs. This is unlikely to provide sufficiently flexibility in today's market place. T.3.2 IP spoofing The scenario proceeds as follows: - User B attaches to GPRS, GGSN allocates IP address, IPB - User B registers in the IMS using his IMS identity, IDB - Attacker A sends SIP messages using his own IMS identity (IDA) but with the source IP address of B (IPB) If the binding between the IP address that the GGSN allocated the UE in the PDP context activation and the source IP address in subsequent packets is not checked then the attacker will succeed, i.e. A pays for IMS service but IP connectivity is fraudulently charged to B. Note that this attack only makes sense for IMS services with outgoing traffic only because the attacker will not receive any incoming packets addressed to the IMS identity that he is impersonating.
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