Mobile app security: threats and best practices

A mobile app runs on devices you do not control, so its code, data, and traffic are all exposed to attackers. This guide covers the main threats, drawn from the OWASP Mobile Top 10, and the practices that defend against them, from secure storage and encrypted traffic to authentication, hardening, and testing.

By Kanika Mathur, Head of Service Delivery

Reviewed by Resourcifi security engineeringPublished Feb 25, 2026Updated Feb 25, 202611 min read

Engineering

Key takeaways

The short version

Mobile apps run on devices you do not control, so assume the code can be inspected, the storage read, and the network watched. Security has to be built in, not bolted on.
The OWASP Mobile Top 10 is the standard checklist of risks: improper credential use, weak authentication, insecure communication and storage, weak cryptography, and thin binary protection lead the list.
The core defenses are encrypt data at rest and in transit (TLS with certificate pinning), store secrets in the platform keystore, use strong token-based auth, and never hardcode keys.
Harden the build against reverse engineering (obfuscation, anti-tamper), validate all input, keep dependencies patched, and enforce least-privilege permissions.
Make security continuous: run SAST, DAST, and dependency scanning in CI/CD, and pen-test before release. Security is a process, not a one-time audit.

The main threats

Most mobile breaches trace back to a short list of well-understood mistakes, catalogued by the OWASP Mobile Top 10. They cluster into a few themes: secrets handled badly, data left unprotected at rest or in transit, weak authentication, and apps that are easy to reverse engineer. The table below maps the leading risk categories to the defense for each.

Leading mobile risks and how to mitigate them
Risk category	What goes wrong	Mitigation
Improper credential usage	Hardcoded keys, secrets in code	Keep secrets server-side or in the keystore; never in the binary
Insecure authentication	Weak or missing auth and session control	Token-based auth (OAuth, JWT), strong session handling
Insecure communication	Unencrypted or unverified traffic, MITM	TLS everywhere plus certificate pinning
Insecure data storage	Sensitive data stored in the clear	Encrypt at rest; use the platform keystore and Keychain
Insufficient cryptography	Weak algorithms or poor key management	Strong, current algorithms and proper key rotation
Weak binary protection	Easy reverse engineering and tampering	Code obfuscation, anti-tamper, root and jailbreak checks
Supply chain and config	Vulnerable libraries, bad defaults	Patch dependencies, scan SBOMs, secure defaults

Attackers have made mobile a primary target. According to the Zimperium 2025 Global Mobile Threat Report, 50% of enterprise mobile devices run outdated operating systems, and mobile-targeted phishing attacks rose 28% year over year, with trojans up 50%. These are not theoretical risks. They play out against real apps shipping to millions of users.

Zimperium, Global Mobile Threat Report, 2025

Protecting data, at rest and in transit

Treat the device as hostile. Encrypt sensitive data at rest using the platform's secure storage, the Keychain on iOS and the Keystore on Android, rather than plain files or preferences, and store as little sensitive data on the device as you can. Encrypt all traffic in transit with TLS, and add certificate pinning so the app only trusts your servers, which blocks man-in-the-middle attacks even on compromised networks. Never log secrets or personal data.

At rest: keystore and Keychain for keys and tokens, encrypted databases for sensitive records, and data minimization so there is less to steal.
In transit: TLS for every call, certificate pinning, and strict validation of the server identity.

Authentication and API security

Authenticate with proven token-based standards such as OAuth 2.0 and short-lived JWTs, refresh tokens carefully, and offer biometric unlock backed by the secure enclave. Treat the mobile app as an untrusted client: enforce all authorization on the server, validate every request, rate-limit and monitor your APIs, and never rely on client-side checks for security. The backend, not the app, is the real security boundary.

Hardening the app

Because anyone can download and decompile your app, raise the cost of attacking it. Obfuscate the code, add anti-tampering and integrity checks, and detect rooted or jailbroken devices where the risk warrants it. Strip secrets and debug code from release builds, request the minimum permissions, and validate all input to prevent injection. These do not make an app unbreakable, but they turn easy attacks into expensive ones.

Testing and CI/CD

Security has to be continuous, not a one-time review. Build it into the pipeline: run static analysis (SAST), dynamic analysis (DAST), secret scanning, and dependency or SBOM checks on every commit, so issues are caught before release. Add regular penetration testing and follow the OWASP Mobile Application Security Verification Standard (MASVS) as the bar. Patch fast when a dependency CVE lands. An app is only as secure as its last release.

Our QA and security engineers build this testing into every mobile app development engagement.

Frequently asked

Mobile app security questions

What is mobile app security?

Mobile app security is the practice of protecting a mobile application, and the data it handles, from threats across the whole stack: the code on the device, the data stored on it, the traffic to your servers, and the backend APIs. Because apps run on devices you do not control, security has to be designed in, covering secure storage, encrypted communication, strong authentication, app hardening, and continuous testing rather than added as an afterthought.

What is the OWASP Mobile Top 10?

The OWASP Mobile Top 10 is a community-maintained list of the most critical mobile application security risks, published by the Open Worldwide Application Security Project. It covers categories such as improper credential usage, insecure authentication and authorization, insecure communication, insecure data storage, insufficient cryptography, weak binary protections, and supply chain and configuration weaknesses. It is the standard reference teams use to prioritize what to defend against, alongside the more detailed OWASP MASVS verification standard.

How do you secure data in a mobile app?

Protect data both at rest and in transit. At rest, store keys and tokens in the platform secure storage, the Keychain on iOS and the Keystore on Android, encrypt sensitive records, and keep as little sensitive data on the device as possible. In transit, encrypt every network call with TLS and add certificate pinning so the app only trusts your servers, which blocks man-in-the-middle attacks. Avoid logging secrets or personal data anywhere.

How do you prevent reverse engineering of a mobile app?

You cannot make an app impossible to reverse engineer, but you can make it expensive. Obfuscate the code, add anti-tampering and integrity checks, and detect rooted or jailbroken devices where the risk justifies it. Crucially, keep secrets and security logic off the client: store keys server-side or in the keystore and enforce all authorization on the backend, so that even if someone decompiles the app they gain little. Hardening raises the cost of an attack rather than eliminating it.

What is certificate pinning?

Certificate pinning is a technique where the app is configured to trust only a specific server certificate or public key, instead of any certificate a device's trust store accepts. This stops man-in-the-middle attacks: even if an attacker installs a rogue certificate on the device or network, the app refuses connections that do not match the pinned certificate. It is a standard defense for protecting sensitive API traffic, and it needs a clear update process so pinned certificates can be rotated.

How do you test mobile app security?

Test continuously and from several angles. In the CI/CD pipeline, run static analysis (SAST), dynamic analysis (DAST), secret scanning, and dependency or SBOM checks on every build. Before release, run penetration testing against the app and its APIs, and verify against the OWASP Mobile Application Security Verification Standard (MASVS). Patch dependency vulnerabilities quickly as they are disclosed. Security testing is ongoing because each new release can introduce new risk.

Kanika Mathur

Head of Service Delivery, Resourcifi

I am Kanika Mathur, Head of Service Delivery at Resourcifi. I make sure security is part of how we scope, build, and test mobile apps, from secure storage and pinned traffic to SAST and DAST in the pipeline and pre-release pen testing. The practices in this guide are the ones our engineers apply on client apps, refined across hundreds of projects since 2017.

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