
SIM Card Security Testing
Master the art of SIM card security testing with comprehensive attack vectors, exploitation techniques, and defense strategies for mobile telecommunications.
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.
Security Landscape Evolution
- 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
- 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

Comprehensive view of SIM card architecture showing hardware components, software layers, and security controls
SIM Card Attack Vectors
Attack Methodology
- Obtain physical access to the target SIM card
- Use a smart card reader to interface with the SIM
- Send carefully crafted RAND challenges to exploit algorithm weaknesses
- Analyze the SRES responses to extract Ki key bits
- Reconstruct the complete 128-bit Ki authentication key
- 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
Vulnerability Status
Exploitation Techniques & Tools
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
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
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
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
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
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
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
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
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
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
Testing Techniques
- Visual inspection and photography
- Side-channel analysis preparation
- Chip decapsulation (invasive testing)
- Interface probing
Required Tools
Testing Techniques
- Smart card interface fuzzing
- Clock and voltage glitching
- Power analysis
- Fault injection
Required Tools
Testing Techniques
- APDU command fuzzing
- Authentication algorithm analysis
- OTA (Over-the-Air) security testing
- SIM Toolkit application testing
Required Tools
Testing Techniques
- Cryptographic algorithm identification
- Key extraction attempts
- Authentication vector analysis
- Known vulnerability testing (COMP128, etc.)
Required Tools
Defense Strategies & Best Practices
- Algorithm Upgrades:
Replace COMP128v1 with MILENAGE or TUAK
- OTA Security:
Implement strong OTA authentication and encryption
- Application Control:
Disable unnecessary SIM Toolkit applications
- Network Monitoring:
Monitor for suspicious binary SMS patterns
- Anomaly Detection:
Track unusual SIM Toolkit activity
- Behavioral Analysis:
Analyze device location and usage patterns
Assessment & Inventory
Audit existing SIM cards and identify vulnerable algorithms
Algorithm Migration
Upgrade to secure authentication algorithms
OTA Hardening
Implement secure OTA update mechanisms
Monitoring Deployment
Deploy security monitoring and detection systems
SIM Security Testing Tools
- • Smart card readers (PC/SC compatible)
- • SIM card adapters and programmers
- • Logic analyzers for interface monitoring
- • Oscilloscopes for side-channel analysis
- • pySim - SIM card management toolkit
- • SIMtrace - SIM protocol analyzer
- • Kraken - A5/1 cryptanalysis tool
- • SIMspider - COMP128 attack tool
- • SMS gateways for OTA testing
- • Binary SMS analyzers
- • Network protocol analyzers
- • SIM Toolkit testing frameworks