GPRS Tunnelling Protocol (GTP) is a workhorse that is essential for all operators. Testing and active monitoring is a must. Emblasoft Evolver can help – find out how in our new briefing paper.

The GPRS Tunnelling Protocol (GTP) has been around for many years and is essential for data connectivity. It’s a workhorse that enables data session communications between retired 2G and 3G networks, while also being fundamental for 4G and 5G networks. It enables internet access, streaming to any device, interconnected roaming, and much more.

Arguably, its Achilles heel is security. It was defined when telecoms networks were proprietary and trusted, closed networks. Times have changed, of course, and so GTP can represents a significant vulnerability, while representing a vital protocol for modern communications.

Why is GTP so important?

For a start, the protocol is complicated, with multiple variants and versions of each. At a high level, GTP works by encapsulating user data in ‘tunnels’, both within and between networks, and can be split into two key areas: GTP-C and GTP-U. GTP-C (GTP-Control Plane) handles tunnel creation, modification, and deletion, mobility management, and session management.

Meanwhile, GTP-User Plane (GTP-U) manages the transmission of user data, such as internet and SMS traffic, between the radio access network and the core network, and within the core network. It enables internet browsing, video calls, and IoT traffic, among other things.

Crucially from a security perspective, GTP also plays an essential role in roaming, and GTP interworking between networks is a key link in the data connectivity chain. As a result, it’s key for enabling seamless mobile data connectivity and user sessions, so monitoring GTP performance and the customer experience it provides is an important task – because your customers expect and demand data access. And quickly complain when they suffer poor experiences.

As well as direct MNO interconnection via GTP, a further consideration is GPRS Roaming Exchanges and Hubs (GRX), which enable MNOs and MVNOs to build indirect roaming interconnection via peers, because they eliminate the need to build individual interconnections with every partner. As a result, testing, assuring, and actively monitoring GTP-based services is a critical, continuous activity.

What are the main GTP vulnerabilities?

There are a number of common GTP vulnerabilities and attacks that operators need to be aware of, including:

• Session Hijacking (Control Plane Exploits) – Used for identity theft, free data usage, or targeted interception.
• Unauthorised Access & Fake Requests – Crafted GTP-C messages that create fake sessions or bypass billing.
• Denial of Service (DoS) via GTP Flooding – The Serving Gateway (SGW) or Packet Gateway (PGW) is overwhelmed with GTP-C Create Session Requests, attackers can cause resource exhaustion.
• User Plane Manipulation (GTP-U Attacks) – Hackers can Inject malicious traffic, impersonate users, redirect sessions, or perform lawful intercept evasion or fraudulent billing bypass.
• Roaming Interconnection Abuse – Mainly down to ‘semi-trustable’ partners, allowing malicious parties to exploit GTP messages sent over inter-operator IPX networks.
• Location Tracking and Subscriber Profiling – Fake GTP requests enable location tracking and potential surveillance.

These attacks are often enabled by weak or absent authentication, directly accessible GTP endpoints, or reliance on legacy architecture, which displays well-known vulnerabilities. Furthermore, with the service-based architecture, virtualisation, and the move to the cloud, 5G offers even more entry points for hackers. How do operators meet this challenge?

How Emblasoft Evolver helps

Emblasoft Evolver provides full support for GTP-C and GTP-U, enabling the modelling of behaviour for different scenarios and network configurations for different kinds of traffic. It supports functional and load testing for all GTP functionality by emulating realistic traffic, including GRX hubs. Evolver also offers active monitoring, providing cost effective assurance for valuable roaming traffic.

Evolver enables MNOs to test and validate performance of GTP on an end-to-end, ongoing basis, helping you to assure performance and close vulnerability gaps – and is used by a growing number of multinational operators.

Find out more by downloading our new briefing paper.