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2G/3G Attacks

Call Interception

CRITICAL SEVERITY
Overview

Call interception attacks enable attackers to eavesdrop on voice communications by capturing and decrypting the audio stream between mobile devices and the network.

Technical Overview

Voice calls in 2G/3G networks use weak encryption (A5/1, A5/2) that can be broken in real-time. Attackers use IMSI catchers or fake base stations to position themselves as man-in-the-middle, capturing the encrypted audio stream and decrypting it using known vulnerabilities.

Impact
Potential consequences of this attack
  • •Complete loss of voice communication privacy
  • •Exposure of confidential business discussions
  • •Personal privacy violations
  • •Intelligence gathering and espionage
  • •Blackmail and extortion opportunities
Attack Vectors
Methods used to execute this attack
  • •IMSI catcher deployment for call capture
  • •A5/1 encryption breaking for decryption
  • •Fake BTS for man-in-the-middle positioning
  • •SS7 exploitation for call redirection
  • •Baseband processor exploitation
Attack Methodology
Step-by-step attack execution process
  1. 1Deploy IMSI catcher or fake BTS
  2. 2Force target device connection
  3. 3Capture encrypted voice stream
  4. 4Break A5/1 encryption using rainbow tables
  5. 5Decode and record voice communications
  6. 6Optionally relay to legitimate network for stealth
Mitigations & Defense
Protective measures and countermeasures
  • Use encrypted VoIP applications (Signal, WhatsApp calls)
  • Upgrade to 4G/5G with stronger encryption
  • Disable 2G/3G when not needed
  • Use IMSI catcher detection apps
  • Implement end-to-end encrypted voice solutions
  • Monitor for forced network downgrades
Real-World Examples
Known incidents and use cases
  • →Law enforcement wiretapping operations
  • →Corporate espionage during negotiations
  • →Government surveillance of journalists
  • →Criminal interception for blackmail
  • →Intelligence agency operations

Related Attacks

2G/3G Attacks
IMSI Catching

IMSI catchers are rogue base stations that trick mobile devices into connecting to them, allowing attackers to capture International Mobile Subscriber Identity (IMSI) numbers and intercept communications.

2G/3G Attacks
A5/1 Encryption Breaking

A5/1 is the encryption algorithm used in 2G GSM networks. Due to its weak 64-bit key and known vulnerabilities, it can be broken in real-time to decrypt voice calls and SMS messages.

2G/3G Attacks
Fake BTS Attacks

Fake Base Transceiver Station (BTS) attacks involve deploying rogue cell towers that impersonate legitimate network infrastructure to intercept communications and perform man-in-the-middle attacks.

References & Further Reading