Telco Security

ISDN Exploits Database

Comprehensive database of ISDN exploitation techniques targeting Q.921/Q.931 protocols

Exploitation Techniques

Q.921 TEI Manipulation Exploit
Exploits Terminal Endpoint Identifier (TEI) assignment vulnerabilities to gain unauthorized network access
HighData Link Layer

Impact

Unauthorized network access, call interception, service disruption

Attack Sequence

  1. 1Monitor D-channel traffic to identify active TEI values
  2. 2Craft malicious TEI assignment request with target TEI
  3. 3Send TEI assignment response to claim target identity
  4. 4Establish unauthorized connection using hijacked TEI
  5. 5Maintain persistence through periodic TEI refresh

Required Tools

  • ISDNAnalyzer
  • Custom Q.921 injector
  • Wireshark with ISDN support

Mitigation Strategies

  • ✓Implement TEI assignment authentication
  • ✓Monitor for duplicate TEI assignments
  • ✓Use encrypted signaling where possible
  • ✓Regular TEI assignment auditing
Q.931 Call Setup Hijacking
Intercepts and manipulates Q.931 call setup messages to redirect or hijack active calls
CriticalNetwork Layer

Impact

Call redirection, eavesdropping, toll fraud

Attack Sequence

  1. 1Monitor Q.931 SETUP messages on D-channel
  2. 2Identify target call reference value
  3. 3Craft malicious CONNECT message with attacker endpoint
  4. 4Send CONNECT before legitimate endpoint responds
  5. 5Establish call redirection to attacker-controlled destination

Required Tools

  • Q.931 Message Crafter
  • ISDN Call Interceptor
  • Custom signaling tools

Mitigation Strategies

  • ✓Implement call setup authentication
  • ✓Use cryptographic call reference validation
  • ✓Monitor for duplicate CONNECT messages
  • ✓Implement timing-based call setup validation
D-Channel Flooding Attack
Overwhelms ISDN D-channel with excessive signaling traffic to cause service disruption
HighDenial of Service

Impact

Service denial, call blocking, network instability

Attack Sequence

  1. 1Calculate maximum D-channel signaling capacity
  2. 2Generate high-volume legitimate-looking signaling traffic
  3. 3Flood D-channel with SETUP/RELEASE message pairs
  4. 4Monitor network response and adjust attack rate
  5. 5Maintain attack to prevent legitimate call establishment

Required Tools

  • ISDN Traffic Generator
  • D-Channel Flooder
  • Network monitoring tools

Mitigation Strategies

  • ✓Implement rate limiting on signaling messages
  • ✓Deploy signaling traffic monitoring
  • ✓Use admission control mechanisms
  • ✓Implement source-based filtering
SPID Authentication Bypass
Spoofs Service Profile Identifier (SPID) to bypass authentication and gain unauthorized access
HighAuthentication

Impact

Unauthorized network access, service theft, identity spoofing

Attack Sequence

  1. 1Analyze legitimate SPID authentication exchanges
  2. 2Identify SPID format and validation mechanisms
  3. 3Craft spoofed SPID with valid format but unauthorized identity
  4. 4Initiate authentication exchange with spoofed SPID
  5. 5Establish unauthorized network access upon successful authentication

Required Tools

  • SPID Generator
  • ISDN Terminal Emulator
  • Authentication bypass tools

Mitigation Strategies

  • ✓Implement cryptographic SPID validation
  • ✓Use multi-factor authentication
  • ✓Monitor for suspicious SPID patterns
  • ✓Implement SPID blacklisting mechanisms
B-Channel Data Interception
Intercepts and captures data transmitted over ISDN B-channels including voice and data communications
CriticalData Interception

Impact

Data theft, voice interception, privacy violation

Attack Sequence

  1. 1Identify active B-channel assignments through D-channel monitoring
  2. 2Establish passive tap on target B-channel
  3. 3Capture and decode B-channel data streams
  4. 4Reconstruct voice calls or data sessions
  5. 5Extract sensitive information from captured traffic

Required Tools

  • B-Channel Tap
  • ISDN Data Decoder
  • Voice reconstruction tools

Mitigation Strategies

  • ✓Implement end-to-end encryption
  • ✓Use secure voice protocols
  • ✓Monitor for unauthorized taps
  • ✓Implement physical security measures

ISDN Security Tools

ISDNAnalyzer Pro
Professional ISDN protocol analyzer with Q.921/Q.931 decoding
Analysis

Features:

  • •Real-time protocol decoding
  • •Call flow visualization
  • •Error detection
Q.931 Message Crafter
Tool for crafting and injecting custom Q.931 signaling messages
Exploitation

Features:

  • •Message template library
  • •Custom IE support
  • •Timing control
ISDN Security Scanner
Automated vulnerability scanner for ISDN networks
Assessment

Features:

  • •Vulnerability detection
  • •Configuration analysis
  • •Reporting
Related Resources
→ ISDN Attack Vectors Overview→ SIGTRAN Protocol Attacks→ SS7 Attack Techniques→ Security Testing Methodology