SIM Card Security Background

SIM Card Security Testing

Master the art of SIM card security testing with comprehensive attack vectors, exploitation techniques, and defense strategies for mobile telecommunications.

Smart Card Security
Hardware Analysis
OTA Security
Cryptographic Attacks
8
Attack Vectors
10
Exploits
6
Testing Phases
15+
Security Tools

SIM Card Security Overview

Subscriber Identity Module (SIM) cards serve as the cornerstone of mobile network authentication, housing critical subscriber identity information, authentication keys, and network-specific applications. As secure elements engineered to safeguard cryptographic secrets, SIM cards implement sophisticated security mechanisms, yet they remain susceptible to both physical and logical attack vectors.

Understanding SIM card security is paramount in today's mobile-centric world, as these diminutive devices establish the root of trust in mobile networks. Compromising SIM security can precipitate severe consequences including identity theft, call interception, SMS manipulation, and unauthorized network access.

Critical Vulnerabilities
  • Legacy COMP128v1 algorithm weaknesses enabling key extraction
  • Insecure Over-the-Air (OTA) update mechanisms
  • Vulnerable SIM Toolkit applications and S@T browsers
  • Side-channel attacks on cryptographic implementations
Modern Protections
  • MILENAGE and TUAK authentication algorithms
  • Enhanced OTA security with proper key management
  • Hardware security modules and secure elements
  • Application isolation and sandboxing

SIM Card Architecture & Components

Hardware Components

Secure Microcontroller

8-bit or 32-bit processor with cryptographic coprocessors

EEPROM/Flash Memory

Non-volatile storage for applications and data (32KB-1MB)

RAM

Volatile memory for runtime operations (1-8KB)

I/O Interface

ISO 7816 contact interface or NFC contactless

Software Stack

Operating System

Proprietary OS with security features and access controls

File System

Hierarchical structure with access control lists

SIM Toolkit

Framework for value-added services and applications

Cryptographic Libraries

Authentication algorithms and encryption functions

SIM Card Security Architecture Diagram

Comprehensive view of SIM card architecture showing hardware components, software layers, and security controls

SIM Card Attack Vectors

COMP128v1 Cryptographic Attacks
Exploiting weaknesses in the legacy COMP128v1 authentication algorithm to extract the secret Ki key
Critical

Attack Methodology

  1. Obtain physical access to the target SIM card
  2. Use a smart card reader to interface with the SIM
  3. Send carefully crafted RAND challenges to exploit algorithm weaknesses
  4. Analyze the SRES responses to extract Ki key bits
  5. Reconstruct the complete 128-bit Ki authentication key
  6. Use extracted Ki to clone the SIM card

Technical Requirements

Hardware
  • • Smart card reader (PC/SC compatible)
  • • SIM card adapter
  • • Computer with card reader software
Software
  • • COMP128 attack tools (SIMspider, Kraken)
  • • Smart card libraries (pyscard, PCSC)
  • • Custom exploitation scripts

Exploitation Techniques & Tools

SIMjacker Exploitation
Exploiting S@T Browser functionality through binary SMS messages
High Complexity
Remote Access

Impact Assessment

Remote surveillance, location tracking, SMS interception, and device manipulation without user awareness

Detection Indicators

  • Unexpected SMS activity from the device
  • Unusual network data usage patterns
  • Battery drain from background activities
  • Unexplained location requests or browser launches
COMP128v1 Key Extraction
Extracting the secret Ki key from SIM cards using COMP128v1 algorithm weaknesses
Medium Complexity
Physical Access

Impact Assessment

Complete compromise of SIM authentication, enabling SIM cloning and unauthorized network access

Detection Indicators

  • Multiple simultaneous network registrations with the same IMSI
  • Calls or SMS received without the device ringing
  • Unexpected location updates in network logs
  • Unusual authentication patterns in network monitoring
OTA Security Bypass
Exploiting weak Over-the-Air update mechanisms to manipulate SIM data
High Complexity
Remote Access

Impact Assessment

Remote modification of SIM data, installation of malicious applications, and unauthorized access to subscriber information

Detection Indicators

  • Unexpected SIM Toolkit application appearances
  • Changes in network registration behavior
  • Unusual binary SMS traffic to the device
  • Unauthorized modifications to SIM configuration
WIB Application Exploitation
Targeting the Wireless Internet Browser application on SIM cards
High Complexity
Remote Access

Impact Assessment

Remote execution of commands, browser manipulation, and unauthorized access to device functions

Detection Indicators

  • Unexpected browser launches
  • Unusual SMS activity
  • Battery drain from background activities
  • Suspicious network connections initiated by SIM
COMP128v1 SIM Card Ki Extraction
Exploits weaknesses in the COMP128v1 algorithm to extract the Ki secret key from a SIM card.
Medium Complexity
Physical access to the SIM card and a smart card reader

Impact Assessment

This exploit allows an attacker with physical access to a SIM card to extract the secret Ki key, which can then be used to clone the SIM card, intercept calls and SMS, or perform other identity theft.

Detection Indicators

  • Physical access to SIM card required
  • Multiple authentication attempts in short succession
  • Same IMSI active in multiple locations simultaneously after exploitation
SIMjacker Exploitation Tool
Demonstrates the SIMjacker attack which exploits the S@T Browser on SIM cards to perform unauthorized operations.
High Complexity
Ability to send SMS messages to the target and a GSM modem or SMS gateway

Impact Assessment

This exploit allows attackers to perform various unauthorized operations on vulnerable SIM cards, including location tracking, sending SMS messages without user knowledge, and executing USSD codes.

Detection Indicators

  • Unusual binary SMS messages containing S@T Browser commands
  • Unexpected device behavior after receiving SMS
  • Suspicious SMS activities in network logs
SIM Card Side-Channel Power Analysis
Extracts cryptographic keys from SIM cards by analyzing power consumption patterns during cryptographic operations.
High Complexity
Physical access to the SIM card and specialized power analysis equipment

Impact Assessment

This sophisticated attack can extract cryptographic keys from SIM cards without leaving evidence of tampering, enabling SIM cloning and complete compromise of mobile communications.

Detection Indicators

  • Physical access to the SIM card required
  • Specialized hardware equipment needed (power analysis setup)
  • No direct network-observable indicators as the attack is purely physical
SIM Swapping Social Engineering Attack
Uses social engineering to convince mobile carrier employees to transfer a victim's phone number to an attacker-controlled SIM card.
High Complexity
Information about the victim and ability to contact their mobile carrier

Impact Assessment

SIM swapping allows attackers to take over a victim's phone number, intercept SMS-based two-factor authentication, and gain unauthorized access to email, financial, cryptocurrency, and social media accounts.

Detection Indicators

  • Sudden loss of cellular service on the victim's device
  • Unexpected 'SIM card changed' or 'phone number transferred' notifications
  • Unauthorized account access alerts
  • Password reset emails not initiated by the victim
SIM Card Fault Injection Attack
Uses precisely timed voltage glitches to disrupt SIM card operations and bypass security controls.
High Complexity
Physical access to the SIM card and specialized fault injection equipment

Impact Assessment

Fault injection can bypass PIN verification, access protected files, extract sensitive data, and manipulate SIM card security controls, potentially leading to complete compromise of the SIM card.

Detection Indicators

  • Physical access to the SIM card required
  • Specialized fault injection equipment needed
  • Potential SIM card malfunction after repeated glitching attempts
  • No direct network-observable indicators as the attack is purely physical
eSIM Profile Hijacking
Exploits vulnerabilities in the Remote SIM Provisioning (RSP) process to hijack eSIM profiles.
High Complexity
Network access and ability to intercept eSIM provisioning traffic

Impact Assessment

eSIM profile hijacking allows attackers to clone a victim's mobile identity without physical access to their device, enabling call/SMS interception, account takeovers, and bypassing SMS-based authentication.

Detection Indicators

  • Unexpected profile download or deletion notifications
  • Loss of mobile service on the victim's device
  • Multiple devices using the same mobile identity simultaneously
  • Unusual activity in eSIM management portals

SIM Security Testing Methodology

4
Testing Phases
15+
Security Tools
50+
Test Cases
1
Physical Analysis
Examining the physical characteristics and security features of SIM cards.

Testing Techniques

  • Visual inspection and photography
  • Side-channel analysis preparation
  • Chip decapsulation (invasive testing)
  • Interface probing

Required Tools

Digital microscope
Decapsulation equipment
Probe station
2
Electrical Interface Testing
Testing the SIM card's electrical interfaces for vulnerabilities.

Testing Techniques

  • Smart card interface fuzzing
  • Clock and voltage glitching
  • Power analysis
  • Fault injection

Required Tools

ChipWhisperer
Smart card reader
Logic analyzer
Power trace analyzer
3
Protocol-Level Testing
Testing the communication protocols and authentication mechanisms.

Testing Techniques

  • APDU command fuzzing
  • Authentication algorithm analysis
  • OTA (Over-the-Air) security testing
  • SIM Toolkit application testing

Required Tools

Osmocom SIMtrace
pySim
SIM Toolkit testing suite
RainbowCrack
4
Cryptographic Analysis
Analyzing and testing the cryptographic implementations.

Testing Techniques

  • Cryptographic algorithm identification
  • Key extraction attempts
  • Authentication vector analysis
  • Known vulnerability testing (COMP128, etc.)

Required Tools

Kraken (A5/1 cracking)
SIMspider
Rainbow tables
Custom cryptanalysis scripts

Defense Strategies & Best Practices

Preventive Measures
  • Algorithm Upgrades:

    Replace COMP128v1 with MILENAGE or TUAK

  • OTA Security:

    Implement strong OTA authentication and encryption

  • Application Control:

    Disable unnecessary SIM Toolkit applications

Detection & Monitoring
  • Network Monitoring:

    Monitor for suspicious binary SMS patterns

  • Anomaly Detection:

    Track unusual SIM Toolkit activity

  • Behavioral Analysis:

    Analyze device location and usage patterns

Security Implementation Roadmap
Step-by-step approach to improving SIM security
1

Assessment & Inventory

Audit existing SIM cards and identify vulnerable algorithms

2

Algorithm Migration

Upgrade to secure authentication algorithms

3

OTA Hardening

Implement secure OTA update mechanisms

4

Monitoring Deployment

Deploy security monitoring and detection systems

SIM Security Testing Tools

Hardware Tools
  • • Smart card readers (PC/SC compatible)
  • • SIM card adapters and programmers
  • • Logic analyzers for interface monitoring
  • • Oscilloscopes for side-channel analysis
Software Tools
  • • pySim - SIM card management toolkit
  • • SIMtrace - SIM protocol analyzer
  • • Kraken - A5/1 cryptanalysis tool
  • • SIMspider - COMP128 attack tool
Network Tools
  • • SMS gateways for OTA testing
  • • Binary SMS analyzers
  • • Network protocol analyzers
  • • SIM Toolkit testing frameworks

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