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Why the basics beat the exotic
Founders picture app security as defending against sophisticated attackers. The reality is less cinematic: the overwhelming majority of real-world mobile incidents come down to basics not done — credentials in plain storage, secrets in the binary, APIs that trust whatever the client sends, and stale dependencies with known CVEs. That's actually good news. It means a disciplined pass over ten controls — the ones in the audit above — removes most of your real-world risk, without a security team on payroll.
The three layers that matter
On the device
Assume the phone is lost, rooted or hostile. Tokens and sensitive data belong in the Keychain (iOS) / Keystore (Android), never AsyncStorage or files. Ship no secrets in the bundle — anything in the binary can be extracted by decompiling. Add code obfuscation for high-value targets, but treat it as a speed bump, not a wall.
In transit
HTTPS everywhere with modern TLS is table stakes; certificate pinning adds protection against man-in-the-middle interception for high-stakes apps (fintech, health). Never disable certificate validation "temporarily" in development — those flags have a way of shipping.
On the server
This is where the real security lives, because it's the only layer you fully control. Authorize every endpoint server-side — check not just "is this user logged in" but "may this user touch this resource." Validate and sanitize all input on the server regardless of client checks. Rate-limit auth and expensive endpoints. Keep an audit trail of sensitive operations. Our fintech work (see FinTech app development) lives and dies by this layer.
What to do with your score
- 80–100: solid foundation — keep dependencies moving and consider a periodic external review to stay honest.
- 50–79: you have real gaps, but fixable ones. Prioritise anything touching tokens, secrets and server-side auth first — they're the breach-makers.
- Below 50: treat hardening as this sprint's work, not backlog. The fixes are well-understood engineering, and most take days, not months.
Security isn't a one-time gate — every new feature, dependency and integration shifts the surface. Re-run this audit quarterly, and after any major release. And remember the flip side: users increasingly choose apps that take their data seriously; both stores now force you to declare exactly what you collect (see the privacy section of our app store launch checklist).
Frequently asked questions
What are the most important mobile app security measures?
HTTPS everywhere with modern TLS, tokens in the platform's secure storage, server-side authorization on every endpoint, no secrets in the app bundle, dependency scanning in CI, and server-side validation of all input. Most real-world breaches trace back to one of these basics.
Where should a mobile app store auth tokens?
In the iOS Keychain or Android Keystore (or EncryptedSharedPreferences) — never plain AsyncStorage, localStorage or files. Secure storage encrypts at rest and gates access, so a lost device doesn't leak sessions.
Is it safe to put API keys inside a mobile app?
No — anything in the binary can be extracted. Third-party secrets belong on your server behind an API you control, with per-user auth and rate limits.
How often should dependencies be updated?
Continuously — automated scanning (npm audit, Dependabot or similar) in CI on every build, with security patches applied promptly. Known CVEs in stale libraries are the most preventable compromise vector.
Can you run a security review of our app?
Yes — we review React Native apps and their backends against this checklist and OWASP mobile guidance. Take the self-audit above, then book a free call and bring your score.