As mobile apps have become a primary target for hackers, mobile application penetration testing has emerged as a critical part of cybersecurity. However, mobile app pentesting differs significantly from its web app counterpart, probing a unique attack surface that encompasses local and server-side elements across iOS and Android devices. In this guide, we’ll delve into the essentials of mobile attack surfaces, vulnerabilities, and pentesting methodologies.
Defining Mobile Application Penetration Testing
Mobile application penetration testing is a type of offensive security that simulates attacks on mobile apps to uncover vulnerabilities that real attackers might exploit and to recommend remediations. It probes vulnerabilities in both locally stored code and interfaces to external APIs, distinguishing it from web application pentesting, which focuses on browser-based environments.
The mobile app pentesting process begins with reconnaissance on application workflows, business logic, and attack surfaces. This provides a basis for automated and manual testing on communication channels, traffic exchanges with external endpoints, and interprocess communication (IPC) between isolated app processes. Tests analyze mobile apps dynamically and also review archives and local files.
Mobile app pentesters rely on open-source intelligence (OSINT) and a variety of tools. Key tools include Static Application Security Testing (SAST) and Dynamic Application Security Testing (DAST) apps, as well as reverse-engineering tools.
Mobile app pentests uncover vulnerabilities such as credential misuse, supply chain insecurities, and unsecured authentication processes. Tests assess the impact on data confidentiality, integrity, and availability. Pentesters communicate their findings in reports that prioritize vulnerabilities and recommend mitigations. Initial tests can be followed by additional tests to assess the effectiveness of the fixes.
The Unique Mobile App Attack Surface
The distinct character of the mobile app attack surface stems from its unique composition. Mobile application security rests on four pillars corresponding to the elements of mobile apps:
- Locally stored data at rest on devices, which includes secrets and keys, intellectual property, personally identifiable information (PII), and business data
- App binary code, which can be in transit during download or at rest on devices
- Network communication data in transit flowing in and out of devices, as well as code protecting this data, including resource connection, authentication, authorization, data validation, encoding, and activity logging
- Backend server-side APIs connecting the app’s user interface with servers, databases, and business logic
Each component of the mobile app attack surface offers hackers opportunities to exploit vulnerabilities. Insecure data storage, unprotected binary code, weak authentication and encryption, and API security gaps all represent risks. Effective pentesting must cover all these attack avenues and identify the greatest risks posed by uncovered vulnerabilities.
Key Differences: iOS vs. Android App Testing
With Android and iOS collectively dominating 99% of the global market, mobile app pentesting primarily focuses on these two platforms. The differences between their respective security architectures necessitate differing approaches to pentesting:
- Android operates within an open ecosystem where APK files can be downloaded from third-party sources, whereas iOS functions in a closed “walled garden” ecosystem with tighter restrictions on third parties
- Android uses a flexible, file-based storage system that allows external SD card support, while iOS uses sandboxed, internal storage management
- Android is more vulnerable to hardcoded credential exposure, permissions management flaws, app tampering, and external storage exploits, while iOS may be susceptible to sandbox jailbreaking, binary vulnerabilities, data leakage from insecure Keychain storage, and insecure API integrations
These differences make it advisable to work with a pentesting partner who specializes in the type of platform you use for your app.
The OWASP Mobile Top 10 Framework
Regardless of platform, certain types of vulnerabilities are common across mobile apps. The Open Worldwide Application Security Project (OWASP) maintains a Top 10 Mobile Risks knowledge base that tracks the most common vulnerabilities, their causes, and their mitigations.
The most recent update lists these as today’s most common vulnerabilities:
- Improper Credential Usage
- Inadequate Supply Chain Security
- Insecure Authentication/Authorization
- Insufficient Input/Output Validation
- Insecure Communication
- Inadequate Privacy Controls
- Insufficient Binary Protections
- Security Misconfiguration
- Insecure Data Storage
- Insufficient Cryptography
Mobile App Pentesting Stages
To probe for these types of mobile app vulnerabilities, pentesters use a six-step process:
- Reconnaissance: gathering information about app workflows, business logic, and attack surfaces
- Automated and manual testing: identifying vulnerabilities by using automated scans and manual techniques to dynamically assess mobile apps, archives, and local files for vulnerabilities in communication channels, traffic between apps and external endpoints, and interprocess communication between isolated app processes
- Exploitation: probing vulnerabilities for impact on app confidentiality, integrity, and availability
- Reporting: providing testing results listing vulnerabilities, ranking their severity, and recommending remediations
- Remediations: implemented recommended fixes
- Retesting: verifying the effectiveness of remediations
Periodic retesting enables iterative, continuous improvements in mobile app security.
Methodology: Static vs. Dynamic Analysis
During the pentesting process, testers use two primary techniques to probe mobile app vulnerabilities:
- Static Analysis: Deploying SAST tools to examine source code or compiled binary without running the app
- Dynamic Analysis: Deploying DAST tools in a sandbox simulation of a real-world environment to test apps in runtime and observe data flow and memory usage
Static analysis helps uncover vulnerabilities overlooked in manual code reviews, particularly susceptibility to SQL injection, buffer overflows, and insecure data storage. Dynamic analysis exposes vulnerabilities to attack vectors such as insecure input validation and broken certificate pinning.
Common Vulnerabilities in Mobile Apps
What are some of the common vulnerabilities that mobile app pentests uncover? A number of underlying mistakes permeate the OWASP Top 10 Mobile Risks we’ve covered. Here are a few of the most common “gotchas”:
- Hardcoded API keys
- Use of insecure code repositories
- Lax authentication processes
- Failure to apply data validation and sanitization
- Lack of SSL pinning
- Insufficient obfuscation of sensitive data
- Oversight of data integrity checks
- Misconfiguration of default settings and permissions
- Sensitive information leakage through unsecured system logs or device caches
- Encryption mistakes
Other vulnerabilities are specific to Android or iOS apps. For example, Android apps are vulnerable to storing unsecured data on SD cards.
The Final Report and Remediation
Mobile app pentesting culminates in a report presenting a prioritized list of vulnerabilities with reproduction steps. Reports include step-by-step remediation guidance for fixing vulnerabilities and recommendations for improving the overall security posture. Pentesting reports aim to provide developers with actionable fixes to harden apps before new releases.
Learn More about Pentesting from the Cobalt Learning Center
Mobile application penetration testing represents one variety of the growing range of specializations within offensive security. To learn more about other types of pentesting and other OffSec topics, visit the Cobalt Learning Center.
