As the mobile network subscriber base exponentially increases due to some attractive offerings
such as anytime anywhere accessibility, seamless roaming, inexpensive handsets with sophisticated
applications, and Internet connectivity, the mobile telecommunications network has now become
the primary source of communication for not only business and pleasure, but also for the many life
and mission critical services. This mass popularisation of telecommunications services has resulted
in a heavily loaded Signaling System number 7 (SS7) signaling network which is used in Second
and Third Generations (2G and 3G) mobile networks and is needed for call control and services
such as caller identity, roaming, and for sending short message servirces. SS7 signaling has enjoyed
remarkable popularity for providing acceptable voice quality with negligible connection delays, pos-
sibly due to its circuit-switched heritage. However, the traditional SS7 networks are expensive to
lease and to expand, hence to cater for the growing signaling demand and to provide the seamless
interconnectivity between the SS7 and IP networks a new suite of protocols known as Signaling
Transport (SIGTRAN) has been designed to carry SS7 signaling messages over IP.
Due to the intersignaling between the circuit-switched and the packet-switched networks, the mo-
bile networks have now left the “walled garden”, which is a privileged, closed and isolated ecosystem
under the full control of mobile carriers, using proprietary protocols and has minimal security risks
due to restricted user access. Potentially, intersignaling can be exploited from the IP side to disrupt
the services provided on the circuit-switched side.
This study demonstrates the vulnerabilities of SS7 messages to cyber-attacks while being trans-
ported over IP networks and proposes some solutions based on securing both the IP transport and
SCTP layers of the SIGTRAN protocol stack
