Industry experts have been sounding the alarm for some time about the security vulnerabilities of the SS7 protocol widely used as the signaling basis for fixed and mobile (2G/3G) networks.
The emergence of 4G has not reduced the level of alarm. It is true that 4G has driven widespread adoption of Diameter and SIP as the new primary signaling mechanisms for mobile networks. However, rather than resolving signaling security concerns, this has amplified those concerns, driven by the allIP nature of SIP (and Diameter). This has been shown to make SIP vulnerable to a wide range of security exploits over and above those besetting SS7 and Diameter. Fraudsters worldwide are gleefully, creatively and vigorously exploiting this fact.