Quick answer: Mobile application security is protecting iOS and Android applications against reverse engineering, data leakage and unauthorized access attacks. Unlike a web application, the mobile application's code and data are directly on the attacker's device; so the application can be opened and examined. The most common flaws are: secrets and API keys embedded in the application, sensitive data stored insecurely on the device, weak or missing server side validation, and insufficient protection against traffic interception. The root fix is to embed no secret in the client, store sensitive data securely on the device, make all critical decisions on the server side and protect traffic with certificate pinning. OWASP MASVS is an international reference framework for mobile security.

When you publish a mobile application, you distribute your code to millions of devices. An attacker downloads this application, opens it and examines everything inside. So mobile security covers both the device side and the server side of the application. This article explains mobile application flaws and the correct defense.

Why a mobile application is a different attack surface

In a web application the code stays on the server; in a mobile application the code and data are on the attacker's device. The attacker can open the application with reverse engineering, read the text and logic inside, and change its behavior while running. So trusting the client is a fundamental mistake: everything on the device must be considered visible and changeable.

The most common mobile flaws

Flaw What it does Result
Embedded secret API key, token in the application Access to the backend via a leaked secret
Insecure data storage Sensitive data stored in plain Data disclosure when the device is compromised
Client side decision Authorization checked on the device Server validation bypassed
Weak traffic protection No certificate pinning Reading traffic with a man in the middle
Reverse engineering The application is opened, logic read Discovery of business logic and hidden endpoints

An embedded secret is the most common and most dangerous flaw on mobile: an API key embedded in the application can be extracted by anyone who opens the application. The client is never a safe place to keep a secret.

The server side, the real line of defense

The most common mistake in mobile security is leaving critical controls to the client. If decisions such as price, authorization, discount or access are made on the device, the attacker bypasses them by changing the application. All critical decisions must be made and validated on the server side. The mobile application's backend API must be evaluated within the OWASP API Security Top 10, and authorization enforced at the object and function level.

Data storage and traffic on the device

When the device is lost or compromised, the data the application keeps on the device falls into the attacker's hands. Sensitive data must not be stored in plain and the device's secure storage mechanisms must be used. Traffic must be protected with certificate pinning; otherwise the attacker on the same network can become a man in the middle and read the traffic. When device forensics is needed, mobile forensics tools also show how possible it is to reach this data.

The correct defense

1. Do not embed secrets in the client

No API key, token or secret logic must be embedded in the application. The client must be considered openable and readable.

2. Make critical decisions on the server

All critical decisions such as price, authorization and access must be made and validated on the server side. No value sent by the client must be blindly trusted.

3. Secure data storage

Sensitive data kept on the device must be protected with the operating system's secure storage mechanisms. Unnecessary data must not be stored at all.

4. Certificate pinning

Traffic between the application and the server must be protected with certificate pinning, and interception with a man in the middle prevented.

Mobile application testing with KAOS

DSET's local AI security engine KAOS tests iOS and Android applications within the OWASP MASVS framework with an evidence first approach. It opens the application with reverse engineering to detect embedded secrets and insecure storage, tries authorization gaps in the backend API and tests traffic protection. It verifies whether a flaw actually leads to sensitive data or unauthorized access and reports only exploitable findings without false positive noise. Because KAOS runs offline, your application and its data are not sent to external services.

Frequently asked questions

Is the API key I embedded in my application safe? No. A key embedded in the application can be extracted by anyone who downloads and reverse engineers it. The client is not a safe place to keep a secret; keys must be kept on the server side and managed from the backend.

Why should I not do critical controls on the client? Because the attacker can change the application on the device. If a price, authorization or access decision is made on the device, the attacker bypasses it. All critical decisions must be made and validated on the server side.

What is OWASP MASVS? The OWASP Mobile Application Security Verification Standard is an international verification framework for mobile application security. It defines requirements in areas such as data storage, cryptography, authentication, network communication and resilience, and provides a common reference for mobile testing.

Sources

To test your iOS and Android application for embedded secrets, data storage and authorization within the OWASP MASVS framework with a working proof, contact DSET. We provide mobile penetration testing and secure code review from our Ankara Hacettepe Teknokent laboratory.