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2G/3G Attacks

SMS Interception

HIGH SEVERITY
Overview

SMS interception attacks allow attackers to capture, read, and potentially modify text messages sent between mobile devices, compromising the confidentiality and integrity of SMS communications.

Technical Overview

SMS messages in 2G/3G networks are often unencrypted or weakly encrypted, making them vulnerable to interception. Attackers can use IMSI catchers, fake base stations, or SS7 vulnerabilities to intercept SMS messages in transit.

Impact
Potential consequences of this attack
  • Exposure of sensitive personal communications
  • 2FA/OTP bypass for account takeover
  • Business intelligence gathering
  • Privacy violations and surveillance
  • Financial fraud through SMS banking
Attack Vectors
Methods used to execute this attack
  • IMSI catcher deployment for local interception
  • SS7 network exploitation for remote interception
  • Fake BTS for man-in-the-middle attacks
  • SIM swap attacks to receive SMS
  • Malware on device for SMS access
Attack Methodology
Step-by-step attack execution process
  1. 1Deploy IMSI catcher or fake BTS in target area
  2. 2Force target device to connect to rogue station
  3. 3Intercept SMS messages during transmission
  4. 4Decrypt if encrypted with weak algorithms
  5. 5Optionally forward to legitimate network to avoid detection
  6. 6Store and analyze intercepted messages
Mitigations & Defense
Protective measures and countermeasures
  • Use end-to-end encrypted messaging apps instead of SMS
  • Implement app-based 2FA instead of SMS OTP
  • Enable RCS with encryption where available
  • Use IMSI catcher detection tools
  • Monitor for unusual SMS delivery delays
  • Educate users about SMS security limitations
Real-World Examples
Known incidents and use cases
  • SS7 attacks on banking 2FA systems
  • Government surveillance of activists
  • Corporate espionage through SMS monitoring
  • Cryptocurrency theft via SMS 2FA bypass
  • Political campaign intelligence gathering