At first glance, a mobile network might appear to be just another way to deliver internet connectivity. But from a security and architectural standpoint, mobile networks are an entirely different ecosystem—riddled with legacy protocols, implicit trust assumptions, radio exposure, and subscriber-centric identity models. These factors make mobile networks both uniquely complex and uniquely vulnerable.
This article outlines the structural, technical, and operational differences that set mobile networks apart—and why those differences demand a dedicated approach to security.
1. Legacy Protocols Still Power the Core
Unlike IT environments that have evolved away from outdated protocols, mobile networks still rely heavily on technologies designed decades ago:
- SS7 (Signaling System 7): A signaling protocol introduced in the 1970s, still widely used in 2G and 3G networks. It was designed for trusted environments and lacks basic security features like authentication and encryption.
- MAP (Mobile Application Part): Built on SS7, MAP handles critical signaling functions such as location updates, authentication vector exchange, and roaming coordination.
- GTP-C (GPRS Tunneling Protocol – Control Plane): Used in 3G/4G to manage session state between different core components. If left unauthenticated or improperly filtered, GTP-C opens the door to session hijacking, denial-of-service attacks, and impersonation.
These protocols remain operational not because they are secure, but because they are embedded into the telco ecosystem—and replacing them is non-trivial.
2. Radio Interface Is a Default Exposure Point
In traditional networks, attackers typically need internal access or a compromised host. In mobile, the air interface (radio) is wide open:
- Broadcast messages like paging requests and system info blocks (SIBs) can be intercepted by anyone with a software-defined radio.
- IMSI catchers or rogue base stations can impersonate network elements to downgrade connections or extract identities from mobile devices.
- Unsecured fallback mechanisms, such as 2G support, can be leveraged to force users into insecure channels.
This exposure makes mobile networks inherently vulnerable to passive and active attacks from anyone within range—no login, no authentication, no firewall breach required.
3. Roaming Expands the Threat Surface Globally
Roaming is one of the most misunderstood and underestimated risks in telecom. It allows mobile users to access services through foreign networks by exchanging signaling messages between their home and visited networks.
The problems stem from:
- Implicit trust: Most roaming signaling is accepted without authentication or verification of sender intent.
- Inconsistent security postures: Some operators implement firewalls and anomaly detection, others do not.
- Protocol fragmentation: Roaming still uses SS7 for 2G/3G, Diameter for 4G, and HTTP/2 in 5G—each with its own quirks and security assumptions.
This effectively turns any malicious or compromised operator into an internal attacker with cross-border reach.
4. Mobile Protocols Don’t Speak Traditional IT
IT teams work with TCP/IP, HTTP, DNS, TLS. Telecom networks? They use:
- Diameter: Introduced to replace SS7, used for authentication, charging, and mobility in LTE networks. TLS support is optional and often unused.
- SIP and IMS Core: Used for voice-over-LTE (VoLTE) and multimedia sessions. SIP has known fuzzing and injection vectors.
- NGAP, S1AP, GTP-U: Essential control and user plane protocols for LTE and 5G, all carrying subscriber-specific metadata and state.
These protocols are stateful, binary, and often vendor-customized, making them invisible to conventional security tools like SIEMs, firewalls, or IDS unless specifically trained.
5. The Subscriber Is the Perimeter
In traditional IT, the perimeter is usually a firewall or access control layer. In telecom, it's the subscriber:
- IMSI (International Mobile Subscriber Identity): The unique identifier that can be exposed during registration or downgrade attacks.
- Authentication vectors (RAND, AUTN, XRES, etc.): Exchanged across the network for validating subscriber access.
- Policy profiles (QoS, APNs, charging): Define what the subscriber can access—and how. Misconfigured profiles can enable unauthorized access or fraud.
If an attacker can spoof, steal, or modify a subscriber’s identity or policy, they can manipulate billing, intercept traffic, or inject malicious content.
6. A Multi-Vendor Patchwork with Poor Isolation
Mobile networks are rarely homogeneous. A typical operator may have:
- One RAN vendor (e.g., Ericsson)
- A different EPC/5GC vendor (e.g., Huawei)
- Third-party probes and analytics systems
- Custom-developed or legacy OSS/BSS platforms
Each interface (S1, N2, S6a, N4) is a potential trust boundary. Many attacks happen at the seams—where protocol assumptions break or vendor logic diverges. Security mechanisms must account for protocol-aware filtering, cross-domain normalization, and granular traffic validation.
7. Security by Obscurity Is Dead
There was a time when telecom security relied on being hard to understand. That time is over.
- 3GPP and IETF specifications are public.
- Open-source implementations (e.g., srsRAN, Open5GS) allow hobbyists to build full network stacks.
- Offensive tools exist for fuzzing SS7, Diameter, GTP, and even HTTP/2-based 5G SBA.
Nation-state actors, cybercrime groups, and security researchers all have the means to discover and exploit mobile vulnerabilities. Security through obscurity is no longer a viable defense model.
8. Heavy Regulation Meets Inconsistent Enforcement
Mobile operators must comply with an alphabet soup of regulations:
- NIS2 (Network and Information Security Directive)
- Cyber Resilience Act (CRA)
- Electronic Communications Code (EECC)
- Lawful Interception and Data Retention Laws
Yet implementations vary widely. Some operators have dedicated telecom SOCs and protocol-specific firewalls. Others rely on outdated intrusion detection and lack telemetry from internal interfaces.
Compliance doesn't equal security—but failing compliance guarantees scrutiny, penalties, and reputational damage.
Conclusion
Mobile networks aren't just different from traditional networks—they’re fundamentally incompatible in how they handle identity, trust, traffic, and risk. They're built on legacy, interconnected by design, exposed through the air, and regulated from every angle.
If you're not treating mobile security as its own domain—with its own tools, telemetry, and threat models—then you're already behind.
The bad guys aren’t waiting for you to catch up.
