No mobile app can be made literally unhackable. You can, however, reduce the chance and impact of compromise by securing the app, its backend, the data moving between them, and the process used to build and test releases. A practical starting point is OWASP’s Mobile Application Security Verification Standard (MASVS), paired with its Mobile Application Security Testing Guide (MASTG).
How should you plan mobile app security?
Start before implementation, not with a final pre-release checklist. Map the app’s sensitive data, the actions an attacker might attempt, the trust boundaries between the app and its services, the third-party components it depends on, and the consequences of a compromised account or device. Include backend APIs in that map: a secure-looking app can still expose data if its services authorize requests incorrectly.
OWASP describes MASVS as the industry standard for mobile app security. It organizes controls into areas including storage, cryptography, authentication, network communication, platform interaction, code, resilience, and privacy. Use the current MASVS guidance to decide which controls apply to your app, then use MASTG to plan how to assess them. Frameworks help structure the work; they do not replace secure architecture, design, or threat modeling.
Turn the threat model into a working scope
- List sensitive data the app collects, processes, sends, or stores, and identify where each copy may persist.
- Identify high-impact actions, such as changing account credentials or payment details, and decide what authentication and authorization they require.
- Mark trust boundaries: the device, app, operating system, backend, third-party services, and any other app or component with which data is shared.
- Record the likely consequences of account takeover, device compromise, data disclosure, or service misuse. Use those consequences to set testing depth and remediation priorities.
How can you reduce sensitive data exposure?
The most effective way to protect data is not to collect or retain it unless the app needs it. Minimize personal information, obtain consent where appropriate, and delete data when it is no longer necessary. Request only permissions required by a feature; a permission that is convenient but not essential expands what the app can access.
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Protect data that must remain on the device
- Keep sensitive files in private app storage and encrypt sensitive data that must be stored.
- Use the platform’s security APIs for storage and cryptographic operations rather than designing your own encryption scheme. Use hardware-backed key facilities when available and appropriate.
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Device storage protections cannot compensate for an app that unnecessarily collects sensitive information or leaves it in secondary locations. Include those less obvious data paths in design reviews and testing.
How should you secure accounts and privileged actions?
Do not treat client-side checks as proof that a user is allowed to perform an action. A determined attacker can alter or bypass logic running on a device. Authenticate users and authorize each sensitive operation on the backend as well as presenting appropriate controls in the app.
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Protect credentials and sessions
- Never hardcode secrets in the app or use a device identifier as proof of identity.
- Issue random, revocable tokens instead of embedding credentials. Store tokens using platform-protected storage, handle expiration, and provide a way to revoke sessions, including through remote logout.
- Require fresh authentication for high-impact operations, such as changing credentials or payment details.
- Biometrics can make authentication more convenient, but provide an appropriate fallback. The app should not receive or expose biometric data.
For every sensitive API operation, the backend should check that the authenticated account is entitled to perform that specific action on the requested resource. A hidden button or a client-side role check is not an authorization boundary.
How do you protect APIs and network traffic?
Use HTTPS for every service connection and leave normal certificate and hostname validation enabled. Do not accept an invalid certificate just to make a connection succeed. Use current, standard cryptographic protocols and ciphers through platform libraries instead of inventing a protocol or cryptographic scheme.
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Review both sides of each API request
- Enforce authorization on the server for every sensitive operation, rather than assuming the app has already checked access.
- Validate input and output so unexpected values do not lead to unsafe processing or disclosure.
- Rotate service tokens or keys that legitimately exist, and avoid placing them in the client where they could be extracted.
- Include network-attack scenarios, including man-in-the-middle testing, in an assessment plan.
Certificate pinning may be considered for a specific threat model, but it is not a substitute for correct TLS configuration. It also creates operational costs: certificate rotation and recovery need to be planned so a pin change does not strand legitimate users.
What platform and release controls matter?
Follow the mobile platform’s security defaults and review how the app interacts with other apps and system features. Pay particular attention to exported components, deep links, inter-app sharing, app groups, and other interfaces where data or actions cross a boundary. Permissions should match actual feature needs, not hypothetical future uses.
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Make secure maintenance part of release work
- Sign releases and use dependencies from sources you trust.
- Monitor dependencies for vulnerabilities and maintain a controlled process for patching and updating the app.
- Review security controls after meaningful changes to features, APIs, dependencies, or platform integration.
- Treat obfuscation and tamper detection as measures that may raise the cost of analysis, not as replacements for backend authorization or sound data protection.
How should you test a mobile app?
Use MASVS to define the controls in scope and MASTG to plan assessment methods and test cases. Testing should cover the app package, its runtime behavior, and the services and network paths it relies on—not just whether the interface behaves as expected.
OWASP’s assessment guidance describes work that can include obtaining and statically analyzing the app package, running the app on a potentially compromised device, and evaluating network attacks such as man-in-the-middle scenarios. MAS-L1 is described by OWASP as an essential baseline recommended for all mobile apps. Its assumptions include a trusted operating system and a primary user who is not an adversary. Those assumptions do not describe every product’s risk; higher-risk apps need an appropriately stronger threat model and assessment scope.
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Choose an assessment scope that matches the risk
A self-assessment, automated tool, or independent assessment can contribute to a security program, but the label alone does not establish what was checked. Ask for a clear scope and compare assessment options using these questions:
- Control coverage: Which MASVS controls and MASTG tests are included, and what is explicitly excluded?
- Testing methods: Does the work cover static analysis, dynamic testing, backend and API behavior, and network security where relevant?
- Version and platform coverage: Which app versions and mobile platforms are in scope?
- Evidence and repeatability: Are findings supported by reproducible steps and enough detail to confirm the issue?
- Remediation: Are findings prioritized by severity, and is retesting included after fixes?
- Confidentiality: How will app packages, credentials, test data, and findings be handled?
Before release, test the controls in scope and resolve findings according to their impact. Repeat relevant checks after meaningful changes; a previous assessment does not establish the security of a changed app or backend.
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