How to Protect Your iOS Apps Against Reverse Engineering

Reverse engineering is the process of analyzing and deconstructing software to understand how it works. Specifically with iOS apps, reverse engineering involves analyzing the compiled binary (machine-readable code) and converting it back into a form that can be more easily understood by humans. This allows attackers to examine the app’s logic, understand how data is processed, and identify potential weaknesses.

Despite common iOS app security misconceptions, iOS apps are not immune to reverse engineering. The robust security measures provided by Apple mainly protect users, rather than the applications themselves. This leaves developers and their organizations exposed to risks that can lead to significant financial and reputational damage.

To stay ahead of these risks, it’s essential to understand the tools and techniques attackers use and how to protect your iOS apps from them. Let’s first explore some of the motivations behind reverse engineering attacks on iOS apps.

Why attackers reverse engineer iOS apps

Reverse engineering allows attackers to gain access to critical parts of an application’s code, enabling them to tamper with the code, steal sensitive data, and even create fake app clones. One primary motivation for reverse engineering is to conduct security analysis. Attackers scrutinize the app's code to identify weaknesses that could lead to the exposure of sensitive data or unauthorized access to backend systems. In some cases, attackers may use reverse engineering to clone an app, creating unauthorized versions that mimic the original’s functionality.

Intellectual property theft is another significant concern, as attackers can extract proprietary code or algorithms embedded in the app. This is particularly damaging for businesses that rely on innovative or unique software to differentiate themselves. Despite the belief that iOS apps are difficult to reverse-engineer, advancements in reverse engineering tools have made the process far easier. Attackers use specialized tools like Hopper and IDA Pro to decompile and analyze iOS binaries, gaining insights into how the app operates. This ease of access means developers must be vigilant in protecting their apps from such attacks.

Let’s explore some of the most popular iOS reverse engineering techniques and tools in more depth.

Tools & techniques used in reverse engineering iOS apps

Attackers commonly use two main techniques to reverse engineer iOS apps: static analysis and dynamic analysis. However, there are a few key considerations that make reverse engineering iOS apps a little more challenging. First, iOS restricts access to system-level functions and debugging tools. As a result, a jailbroken device is necessary to gain full access.

Just because Apple makes it more challenging to reverse engineer apps, doesn’t mean attackers aren’t up to the challenge. Several advanced iOS reverse engineering tools help attackers extract hardcoded secrets, debug private APIs, and bypass security controls. When attackers combine static and dynamic analysis, they can gain deep insights into how an app functions, how data is handled, and where potential vulnerabilities lie.

Here are some examples of how each of these techniques work, along with some tools commonly used in the process.

• Static analysis: Involves examining the app's code without executing it. This technique helps attackers identify susceptibilities, understand data handling, and extract sensitive information. Static analysis tools such as otool, class-dump, and disassemblers like Ghidra or Hopper are critical for inspecting an app’s architecture and internal logic.

  otool is used for examining the binary structure of iOS apps, which are typically compiled for ARM64 architecture, with support for ARMv7 for older devices. Class-dump (which isn't used much and is not actively maintained) helps extract classes, methods, and instance variables from the app's binary, especially for Objective-C code. For Swift code, a variant called class-dump-swift is available. Tools like Ghidra, Hopper, and others allow attackers to disassemble the compiled machine code into human-readable assembly code, making it easier to understand the logic of the application’s code and identify security flaws.

• Dynamic analysis: Involves running the app in a controlled environment (e.g., a jailbroken iOS device) to observe its behavior under different conditions. Tools like Frida, Radare2 and R2Frida (R2Frida is an integration of the two - Frida and Radare2) allow attackers to manipulate the app during runtime, bypassing security features like jailbreak detection. This is especially dangerous, as it enables attackers to intercept calls to functions within the app and modify its behavior.

Common reverse engineering threats for iOS apps

One of the most common techniques in iOS reverse engineering is decompilation. As we referenced above, attackers use tools like Hopper and IDA Pro to reverse the compiled binary into human-readable code.

Somewhat related to decompilation, binary patching is another risk. Attackers modify the app’s binary to change its behavior or introduce malicious code. This allows them to clone the app or modify it in ways that can bypass security features, such as adding backdoors or altering how the app communicates with backend systems. For example, cloned apps were a major threat in India, where attackers created fake banking apps to exploit legitimate banks’ customers.

Another significant threat is data extraction. Attackers can extract critical information, such as cryptographic constants and backend server details, by analyzing how the app handles sensitive data. This technique was at work during the Solana blockchain incident, where attackers extracted sensitive cryptographic keys from a mobile wallet app, resulting in millions of dollars in financial losses.

Strategies to protect iOS apps from reverse engineering

Protecting your iOS app requires a multi-layered approach — in other words, combining various techniques to safeguard your app’s code from reverse engineering. Using this approach protects against both static and dynamic attacks. Let’s explore some of the best security strategies to protect your iOS app throughout the entire mobile app development lifecycle.

Code obfuscation

Code obfuscation is one of the most effective code hardening techniques. By obfuscating the code, you make it difficult for attackers to understand how the app functions. Code obfuscation techniques include:

• String obfuscation: Uses obfuscation to hide sensitive strings and API keys
• Control flow obfuscation: Alters code structure to confuse attackers without changing functionality
• Name obfuscation: Changes class, method, and variable names to nonsensical values
• Arithmetic obfuscation: Converts simple arithmetic and logical expressions into complex equivalents

Encryption

Encryption is another important strategy. By encrypting critical components of the app, you can prevent attackers from easily extracting sensitive information. Encryption also plays a big role in preventing SSL pinning bypass attacks, which are commonly used by attackers to intercept communication between the app and the server. Common encryption techniques include:

• String encryption: Protects sensitive strings (e.g., API keys, passwords etc) by converting them into an unreadable format to prevent easy extraction or manipulation.
• Asset encryption: Secures assets like images, audio, or other media files, preventing unauthorized access or tampering of embedded content.

RASP

Runtime application self-protection (RASP) is a dynamic security measure that monitors the app’s behavior in real time and responds to potential tampering or jailbreak attempts by terminating the app or restricting its functionality.

RASP when combined with obfuscation provides a comprehensive protection to apps. The polymorphic nature of protections also ensure that each new build of the app has a unique set of security checks. This makes it harder for attackers to use old knowledge on newer app versions.

Ongoing mobile app security testing & monitoring

Mobile app security should be an ongoing process, with regular testing, fixing bugs, and monitoring to detect and address them before they can be exploited. For example, the Solana incident mentioned above could have been preventable—a failure to test and update key security measures led to significant financial losses.

Tools for real-time threat monitoring help developers stay ahead of potential security breaches by alerting them to suspicious activity and providing insights into how to mitigate risks. Regular updates to your app's security features, based on the latest threat intelligence, are critical for maintaining the integrity of your app.

Embrace a multi-layered approach to iOS app security

Protecting your iOS app from reverse engineering is an important part of safeguarding your intellectual property, ensuring data security, and preventing financial losses. By combining techniques such as code obfuscation, encryption, RASP, and ongoing security testing and monitoring, you can create a robust defense against attackers. Taking advantage of the right tools and techniques will help you stay ahead of evolving threats — ensuring that your app remains secure even as attacks grow more and more sophisticated.