Telco Security

Telecommunications Signaling Protocols

Comprehensive reference guide to telecommunications signaling protocols, their security vulnerabilities, and protection strategies for modern networks.

Signaling System No. 7
Legacy signaling protocol used in 2G/3G networks for call setup, SMS, and mobility management. Despite its age, SS7 remains widely deployed and is a critical component of global telecommunications infrastructure.
2G/3G

Key Features

  • Call setup and teardown
  • SMS message routing
  • Mobile subscriber roaming
  • Number translation services
  • Billing and charging information

Known Vulnerabilities

Location Tracking

Critical

Exploiting SS7 to track subscriber location in real-time without their knowledge

SMS Interception

Critical

Intercepting SMS messages including one-time passwords and authentication codes

Call Interception

High

Redirecting and intercepting voice calls for eavesdropping

Subscriber Data Theft

High

Unauthorized access to subscriber data including IMSI, MSISDN, and service profiles

Security Measures

  • Implement SS7 firewalls at network borders
  • Deploy message filtering and validation
  • Enable comprehensive signaling monitoring
  • Implement authentication for roaming partners
  • Regular security audits and penetration testing
Diameter Protocol
Successor to RADIUS, used in 4G/5G networks for authentication, authorization, and accounting (AAA). Diameter provides enhanced security features but still faces significant vulnerabilities.
4G/5G

Key Features

  • Authentication and authorization
  • Policy and charging control
  • Subscriber profile management
  • Quality of Service (QoS) enforcement
  • Real-time charging

Known Vulnerabilities

S6a Interface Disclosure

Critical

Exploiting the S6a interface to extract subscriber information from HSS

Command Injection

High

Injecting malicious commands into Diameter message exchanges

Routing Manipulation

High

Manipulating Diameter routing to redirect traffic for interception

Identity Spoofing

Medium

Spoofing network element identities to gain unauthorized access

Security Measures

  • Deploy Diameter Edge Agents (DEA) with security controls
  • Implement end-to-end encryption for sensitive data
  • Enable comprehensive message validation
  • Deploy topology hiding mechanisms
  • Implement strong authentication between network elements
Signaling Transport
Protocol suite for transporting SS7 signaling over IP networks, bridging legacy and modern networks. SIGTRAN enables the transition from circuit-switched to packet-switched signaling.
2G/3G/4G

Key Features

  • SS7 over IP transport
  • Stream Control Transmission Protocol (SCTP)
  • MTP Level 3 User Adaptation (M3UA)
  • SCCP User Adaptation (SUA)
  • Gateway signaling conversion

Known Vulnerabilities

SCTP Vulnerabilities

High

Exploiting vulnerabilities in the Stream Control Transmission Protocol

M3UA Exploitation

High

Exploiting the MTP Level 3 User Adaptation layer for unauthorized access

Gateway Compromise

Critical

Attacking signaling gateways to compromise the boundary between SS7 and IP networks

Security Measures

  • Secure SCTP associations with IPsec
  • Implement gateway-level access controls
  • Deploy comprehensive logging and monitoring
  • Regular security updates for SIGTRAN stacks
  • Network segmentation and isolation
Session Initiation Protocol
Signaling protocol for initiating, maintaining, and terminating real-time sessions for VoIP and multimedia communications. SIP is the foundation of modern IP-based voice and video services.
VoIP/IMS

Key Features

  • Session establishment and termination
  • User location and availability
  • Session parameter negotiation
  • Multimedia session management
  • Presence and instant messaging

Known Vulnerabilities

Registration Hijacking

High

Hijacking SIP registrations to redirect calls and messages

Message Tampering

High

Intercepting and modifying SIP messages to manipulate sessions

Call Eavesdropping

Critical

Intercepting and listening to VoIP calls without authorization

DoS Attacks

Medium

Denial of service attacks against SIP servers and endpoints

Security Measures

  • Implement TLS for SIP signaling encryption
  • Deploy SRTP for media encryption
  • Enable SIP authentication mechanisms
  • Implement rate limiting and DoS protection
  • Regular security audits of SIP infrastructure