Positive Technologies has issued a report on the emerging security problems of 5G signaling networks titled "5G Signaling Networks: Blast From the Past." The title is descriptive of the central thesis of the report, that backwards compatibility will allow the security mistakes of the past to be carried forward into the next generation of mobile usage.
They point out that some of these older threats are quite well known: security researchers have long been discussing vulnerabilities in 2G and 3G networks. Older solutions in use may no longer be valid. For example, traditional two-factor authentication by SMS is no longer recommended for securing critical services.
But a new factor has emerged: the Internet of Things (IoT). The GSMA industry group expects IoT connections to grow from 9.1 billion this year to 25.2 billion in 2025.
One of the underlying problems in 5G signaling is that it continues to rely on Signaling System 7 (SS7). SS7 was designed for a totally different threat model when only fixed-line operators had access to the network. Security was an afterthought.
PT has already issued a report on SS7. It found that SS7 has architectural flaws that allow executing a whole range of attacks, including eavesdropping, SMS interception and fraud.
But SS7 interoperability will remain a 5G parameter for the foreseeable future. PT sums up the reasons for this fairly well: "According to GSMA estimates,1 the user base of 4G/5G subscribers is only starting to approach that of 2G/3G users. The number of 3G users is unlikely to decline significantly until at least 2025. But even at that time SS7 networks will continue to be relevant, since 2G/3G users are projected to account for a quarter of all subscribers (not counting IoT devices)."
4G networks may use the differing Diameter protocol instead of SS7. But they still must interconnect with previous-generation networks. So in practice, these networks, too, are vulnerable to some SS7 attacks.
Today's 5G networks have a non-standalone architecture. They rely on a 4G LTE core network (EPC). This allows improving the bandwidth and latency of user data with a 5G base station connected to existing 4G infrastructure. But any 5G devices while connecting to 5G frequencies for data transmission, will still rely on 4G and even 2G/3G networks for voice calls and SMS messaging.
According to ENISA, more than 80% of the telecom providers have declared having security incidents. To mitigate these, existing security best practices must be followed. Only 30% of operators in the EU have implemented them. In developing countries, fewer than 0.5% have done so.
Though 5G standards are evolving, it is necessary for all stakeholders to be present at their design phase. Only then can security considerations be brought to the forefront, as they should be.
— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.