Page 31 - ITU-T Focus Group Digital Financial Services – Technology, innovation and competition

ITU-T Focus Group Digital Financial Services
Technology, Innovation and Competition

3.6 Mobile network: Network operations

Role within the ecosystem

The carrier network provides transit connectivity for information originating at the customer handset. It
provides the gateway to external providers and to DFS providers, which may be associated with the particular
carrier or may be external entities requiring Internet communication.

Security threats and vulnerabilities

Access control
Insufficient internal controls can allow insider access to customer data. This is particularly important for SMS
and USSD solutions that do not provide encryption within the provider network.

Authentication
Information can be spoofed by insiders, particularly in protocols that provide no notion of message integrity.

Non-repudiation

Without digital signatures, there is no notion of non-repudiation in these networks.

Data confidentiality
The communication link between the mobile base station and the provider network must be secured. In some
cases, this is a wireline link, while in other scenarios, depending on the topography of the mobile network,
the base stations may be connected to the provider network wirelessly, such as through a microwave link.
In many cases, this communication is unencrypted. Particularly for SMS and USSD-based transactions where
encryption is strictly provided through GSM algorithms between the handset and base station, this means
that data could potentially be sent back to the network in the clear, facilitating a breach of confidentiality.

Communication security

Recent attacks against the SS7 protocol have demonstrated that communication is very vulnerable in
unencrypted networks. Tracking users through SS7 hijacking is possible and may have been performed already
in real networks. The Ukrainian Telecom regulator [12] described the intrusion of external SS7 packets into
the network and the potential for location tracking and surveillance as a result.

In the DFS context, a bad actor at the SS7 network level is able to emulate (‘spoof’) the Caller Line ID (CLI) of
a trusted person or entity, and call the DFS customer to attempt to extract DFS and bank credentials from the
customer, ultimately leading to financial loss.

The need to facilitate roaming using SS7 introduces vulnerabilities in these networks and affects the core
network and base stations at the extremieties of the networks. These SS7 vulnerabilities can be exploited via
the SS7 component ‘MAP’ – which in turn powers USSD, one of the primary customer UIs for accessing DFS
around the world.
This SS7-derrived vulnerability is a systemic problem with all USSD-based mobile access systems, ostensibly
allowing a bad actor with relatively basic telecommunications skills to perform dangerous attacks that may
lead to direct customer financial loss, confidential data leakage, or disruption of communication services.
For user security and privacy, it is vital for providers to mitigate the impact of SS7 attacks.

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