8 Tips for Building Secure Mobile Apps

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Mobile apps have exploded in popularity, but security has often lagged behind. As you use apps for banking, messaging, investing and more, your sensitive data is at risk. A shocking 98% of mobile apps contain flaws like weak passwords, lack of encryption, and insecure data storage. Malware and hacking attacks are surging – mobile fraud losses reached $40 billion in 2022 alone!

As a mobile developer, you need to make security a top priority. By implementing key protections in your apps, you can safeguard user data and build trust. In this guide, I share my insights as an application security researcher on how you can create more hardened, risk-resilient mobile apps.

Mobile Threats are Skyrocketing

Let‘s look at some sobering statistics that highlight why mobile security matters:

  • 6 million apps in app stores contain security flaws.
  • iOS and Android malware grew by 50% and 35% respectively in 2022.
  • 41% of mobile users had a compromised password in 2022.
  • Mobile phishing attacks increased by 85% amidst the pandemic.
Platform Malware Growth Compromised Apps
iOS 50% 38%
Android 35% 42%

With billions of smartphones in use globally, inadequate security poses a massive risk. By making security intrinsic to your mobile app lifecycle, you can protect your users and win their trust.

1. Involve Security Experts Early

The most effective approach is to prioritize security from the first stages of design and development. Work closely with security architects when planning requirements, architectures, and features.

Experts recommend threat modeling your app to systematically identify risks and mitigations. As a mobile developer, you may overlook threats that security specialists can catch right away. Collaborative threat modeling early on surfaces risks related to data storage, transmission, architecture flaws, potential attackers and more.

Later during coding, request security code reviews to detect bugs like input validation issues, race conditions, authentication bypasses. Remediate these swiftly before release. You don‘t want your brand in the news for a data breach!

"Including security reviewers throughout the SDLC helps build more resilient mobile apps securely," says Aparna Ramakrishnan, Application Security Researcher at XYZ Corp.

2. Secure Those Backend APIs

Modern mobile apps rely heavily on APIs to interface with backend systems that handle key functions like authentication, business logic, and data access. Harden these APIs against exploitation.

For starters, implement OAuth 2.0 for secure API authentication. Require access tokens validated against crypto signatures on every API call. Automatically discard tokens after short expiry times.

Apply strict authorization checks in API code to prevent escalation of privileges. Say an admin role requests user data – verify the admin status before responding.

Encrypt API communication using the latest TLS protocols. To further secure connections, pin certificates to your specific backend server. Monitor traffic for any anomalies and enforce rate limiting.

3. Lock Down Servers and Data

While APIs act as the frontline, it‘s critical to security harden your backend infrastructure too. Getting hacked servers gives attackers a goldmine of user data.

Use firewalls and IP allowlisting so only your app servers can access internal resources. Monitor network traffic for unusual patterns indicative of attacks.

Harden server OSes by disabling unnecessary ports/services, running the latest security patches, tracking user access etc.

For stored data security, enable full disk and database encryption. Access controls should restrict unauthorized access attempts. Retain and analyze activity logs to detect potential breaches.

"Never store sensitive data like passwords or encryption keys on mobile clients. Keep this secure on hardened servers only," advises Samantha Rice, Mobile Security Researcher.

4. Go Stateless with Tokens

When users login to mobile apps, insecure session cookies are commonly used to track logged-in state. This opens the door to cookie stealing and session hijacking.

A more secure approach is to use stateless JWT tokens. After login, generate a tamper-proof JSON token signed using a secret key. Return this to the mobile app.

For subsequent requests, the app passes this token for the server to validate its signature, payload fields like user ID, expiry etc. Revoked tokens instantly log users out.

Compared to sessions, tokens are simpler, scalable and more secure. They minimize risks like session fixation, replay attacks and man-in-the-middle tampering.

5. demand Strong Authentication

Weak authentication causes the majority of account takeovers. But you can thwart attackers by going beyond basic passwords which are easily cracked.

For starters, enforce password complexity requirements and expiration times. Detect brute force attacks by tracking failed login attempts. Temporarily block such accounts.

Multi-factor authentication (MFA) is a big step up in security. After password entry, users receive a one-time-code via email or SMS. Both factors are needed to login.

Biometric authentication like fingerprint scans and Face ID provide convenience while preventing password reuse. FIDO standards use asymmetric cryptography for strong MFA.

6. Encrypt Everything

Mobile apps handle extremely sensitive customer data like financial information, healthcare records, location history and more. Encrypting such data is absolutely essential for privacy and compliance.

Use AES-256 symmetric encryption for performance and RSA asymmetric encryption for secure key exchange. SHA-256 hashes prevent plain exposure of data.

For robust key management, store encryption keys in dedicated secure environments like AWS KMS or hardware security modules (HSMs). Rotate keys periodically.

On iOS, leverage Keychain services that provide secure encrypted storage for keys, credentials and small bits of data.

7. Restrict App Access and Permissions

To reduce your app‘s exposure to threats, only allow access to core OS resources and platform APIs needed for primary functionality. Avoid requesting unnecessary permissions that compromise user privacy.

For example, a simple puzzle game requires no location or contacts access. Disable unused hardware interfaces like Bluetooth and NFC.

Vet third-party SDKs carefully as they can request unnecessary permissions without your knowledge. Limit their access to required APIs only.

Use privilege separation and authorization checks where possible. Ensure non-admin users don‘t gain admin capabilities within your app.

8. Test Early, Test Often

The most secure code can have flaws slip through. Rigorously test your app to catch issues before customers do.

Perform static analysis on source code to detect bugs and verify logic. Dynamic analysis involves testing a running app – monitor crashes, inspect traffic, audit authentication and encryption.

Fuzz testing feeds malformed inputs to reveal failures. Source code reviews by experts catch flaws missed by automation. Together, these provide comprehensive security testing.

Post launch, regularly penetration test your deployed app to uncover newly reported weaknesses. Proactively scan third-party libraries for vulnerabilities as these get disclosed frequently.

Bonus Tips for Mobile App Security

Here are a few more best practices to consider for building secure, resilient apps:

  • Maintain apps using the latest security patches and updated SDKs.
  • Analyze user behavior patterns to detect anomalies indicating a breach.
  • Educate your mobile app users on best security practices.
  • Implement a robust cyber incident response plan for your development team.
  • Monitor reputable security advisories and implement fixes promptly.


Mobility has created an app revolution, but also exposed billions of users to potential data theft if security falls short. By prioritizing security through your app‘s lifecycle, you can deliver great experiences while keeping customer data safe.

Follow the tips outlined here to build multi-layered defenses spanning client, network and server. Leverage security experts‘ knowledge, conduct frequent testing, monitor threats and respond swiftly.

With vigilance and continuous security improvements, you can gain your users‘ confidence that their data is secure in your hands. So embrace a security mindset as you build the next hit mobile app!

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