Is SMS Secure and Relevant in a 5G World?

We recently released a white paper entitled ‘The Future of Messaging: Securing 5G in SMS’. You may not necessarily think of SMS or text messaging when you think about the future of messaging or indeed 5G security concerns. You may ask, why did our research department decide to delve into this topic and more importantly why does it matter?

Having seen first-hand past and current mobile security threats, our threat intelligence experts recognized the importance of exploring SMS in 5G. There has been a tendency to overlook SMS as a security concern for the next generation of 5G networks as much media focus has been on the security of 5G supply chain and other potential 5G network use case such as the potential vulnerabilities we uncovered with slicing.

Our team wanted to research the critical role that SMS continues to play in the mobile eco-system and highlight potential vulnerabilities, that left unaddressed, could be open to exploitation, seriously threatening the security of nations, networks, enterprises, and subscribers.

Are 5G networks secure?

The 5G networks represent huge opportunities for mobile network operators to boost customer experience and grow revenues. But the technologies within 5G networks also bring significant security risks that need to be addressed now, to secure the future.

One point that there seems to be public consensus on, is the value of the information that will live on 5G networks and the attractiveness of that information to bad actors.

A recent joint CISA/NSA report stated:-“5G networks, which are cloud-native, will be a lucrative target for cyber threat actors who wish to deny or degrade network resources or otherwise compromise information” (CISA/NSA, 2021)

As a mobile and 5G security company, our researchers have already highlighted some key areas of concern around 5G network security. Just last year we published details of a major security flaw in the architecture of 5G Network Slicing and Virtualized Network Functions.

Unfortunately, following our latest research, we now see further possible attack scenarios involving the use of SMS on 5G networks.

Why securing SMS in 5G is so important?

SMS has been an unexpected, but overwhelmingly successful, feature of mobile networks. The latest generation of 5G mobile networks introduces many new features, but no single new feature can ever match the simple reachability of every device in the world via SMS.

The popularity of SMS remains strong

Despite previous predictions around the demise of SMS and the reduction of Person-to-Person (P2P) messaging on the channel; there has been a significant increase in Application-to-Person (A2P) SMS traffic enabling businesses to have digital conversations with their customers. A2P messaging includes provisioning of PIN codes, one-time passwords (OTPs), notifications, chat bots/virtual assistants, appointment reminders, or marketing messages. A recent Global A2P SMS Messaging forecast by analysts Mobilesquared estimates that the spend globally on A2P SMS will grow 87% by 2025.

What are the Advantages of SMS?

SMS’s advantages are the simplicity of use for both customers and retailers and the high return on investment for companies that use it to communicate with their customers. SMS is on all mobile phones, in all parts of the world. You do not have to have a smart phone, download an app or invite contacts to exchange messages. Other messaging apps often referred to as OTT (Over-the-Top) apps, rely on geographical popularity for user downloads. For example, in China, consumers use WeChat but Facebook Messenger is the most commonly-used messaging app in the US.

Also, due the remarkable reachability of SMS, we also see Government and Public institutions increasingly turning to SMS notifications as a way to send important public safety information or alerts. For example, Covid Booster SMS Alerts share by UK Health Body the NHS.

SMS will continue to be supported over 5G and there are even more use cases within 5G for SMS which further makes the case for ensuring security of SMS across the network. One such use case using SMS alerts for IoT devices. Which I will discuss in some detail later in this blog post.

The Future of SMS

SMS Usage: From User to Machine

We already see SMS usage increasingly moving from user centric messaging towards application and machine SMS-based messaging. This highlights further the urgency of securing of SMS communications. When it comes to machine SMS messaging, there is no human “control instance” that could notice a security breach and raise an alert.

SMS being used to enable IoT devices

As mentioned, the usage of mobile networks will transform with 5G and it is very likely that we will see new business cases for SMS in 5G emerge. One example is IoT, the number of IoT devices worldwide is projected to increase to 30.9 billion units by 2025.

This could mean a future of hi-tech life with revolutionary smart cities and homes, connected transport, and connected agricultural/industrial equipment. With many of these devices having sensors connecting to a 5G network. The technology will need a way to communicate with people and other machines to exchange data and alerts externally and SMS is great candidate for communication channel with its ubiquity, global coverage, cost-effectiveness, and power efficiency (SMS requires very little battery). It does appear that SMS will play a key part of enabling the growing market of IoT making it more essential than ever to ensure that SMS is secured especially if being leveraged by industry for critical communications.

What are the 5G security concerns for SMS in 5G?

Our latest white paper goes into full technical detail on how SMS in 5G works breaking down the structure of the 3 approaches to sending SMS over the 5G core network:

  1. SMS over Non-Access Stratum (NAS)
  2. SMS over IP using IP Multimedia Subsystem (IMS)
  3. SMS using Rich Communication Suite (RCS)

Once we analysed the architecture of sending SMS in 5G we could see possible security gaps in several areas:

Integration with Legacy technology

In the next generation of 5G mobile networks, SMS retains and requires legacy infrastructure, which must be integrated with the new technologies 5G brings to the mobile network. As mobile operators will stagger the deployment of 5G networks, we must consider how mobile operators will implement legacy support for SMS traversing both 4G and 5G networks. This makes SMS’s security considerations for the previous generations of mobile networks just as important for 5G. We have already seen SMS security being compromised on the previous mobile network generations, so all of these threats still exist for 5G networks but with even more valuable data for hackers to access.

SMS and Roaming in 5G

Subscriber roaming is another important scenario to think about from a security perspective. In some instances, for phones using 5G roaming, any text messages sent to or from the phone, would actually be converted to or from 2G, 3G or 4G, for use over the inter-operator interface. Essentially mobility control and registration would be handled by 5G protocols, but the sending or delivery of the SMS would be handled by one of the earlier protocols. So again, there are potential security gaps and possible entry points for attackers.

Rich Communication Suite (RCS) in 5G

RCS expands on the current simplicity of SMS messaging and allowing subscribers to have group chats, richer media messaging like images, video, audio, and get read receipts, basically RCS functions like other OTT messaging apps. However, subscriber adoption of RCS has been slow to take off and in 5G scenarios we see SMS being used as fallback, when receiver is unable to support RCS. This means RCS messages will also be impacted by the SMS legacy and roaming points we outlined earlier.

Conclusion: Protecting SMS in 5G

SMS is far from dead. If anything, it has been resurrected and is being leveraged by enterprises for to support digital transformation of businesses. Mobile networks are more vital than ever, to digitally connect subscribers, enterprises, IoT devices and even to support critical national infrastructure. Mobile Network operators have a duty to protect their networks from both existing and evolving attack scenarios (see our post on how MNOs can increase security in SMS). Even with new standards and specifications, the security in 5G is not completely ‘built-in’, and lessons from the vulnerabilities of previous mobile network generations must be learnt and applied to secure the future of SMS mobile messaging in 5G.


Our next blog in this series will further investigate the security risks of SMS and the possible attack scenarios. Looking at the current misuse of SMS and the various attack types that are possible today and that we believe will continue when sending SMS through the 5G core network including: Unsolicited SMS Messaging, SMS Phishing Attacks, Premium SMS Fraud, Mobile Malware, Surveillance, Information Retrieval, Denial of Service, SMS Interception and Grey Routes abuse. We will also share new potential SMS risks and attacks that may arise in the next generation of mobile networks.

Learn more in our white paper:

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