Finding Hooks in Android Applications: Tools for Security Research
Understand how hooking is used by bad actors, how hooking relates to mobile security research, and how you can use tools like Frida for security research.
Android hooking is a powerful technique used to intercept and modify the behavior of Android applications and the Android operating system. As with any technique these days, hooking is used for both legitimate purposes as well as for the malicious manipulation of mobile apps.
As a result, developers and security researchers have a vested interest in being able to find hooks in Android applications, both for building more secure apps and in advanced security testing.
In this article, we’ll review what hooking is, how it’s used by bad actors, and how you can use mobile security research tools to find hooks in mobile apps.
What Is Android Hooking?
Hooks are snippets of code that are used to intercept or modify the behavior of Android applications. In the case of Android self-hooking, the technique is used to obfuscate how an Android application works to protect the contents of the underlying app.
Hooking is used in everything from security products for already built applications to games deploying anti-cheat software. Developers and security researchers use hooking to improve the security of Android applications, debug application code, add new features, and conduct advanced research.
The Malicious Side of Android Hooking
Cybercriminals compromise Android mobile apps by using the same hooking tools and techniques as security researchers. By injecting malicious code, bad actors are able to execute man-in-the-Middle attacks (MitM), malware, and more, leading to data theft and follow-on attacks.
Malware can use hooking to steal sensitive information, including credentials, sensitive data, and personal information, by intercepting keyboard inputs or network traffic. Malware can also use hooking to evade detection that is implemented in certain applications. By intercepting and modifying system calls and API functions, malware can hide its presence and carry out malicious activities undetected. For example, malware can use hooking to bypass implemented security controls including root / jailbreak detection and more.
What Are the Implications for Mobile Security Research and Testing?
From a security research and testing perspective, it’s important to be able to find existing hooks as part of your regular testing to understand how an app functions and how it can be manipulated. Tools like Frida, a dynamic code instrumentation toolkit for developing, researching, and reversing applications, make it much simpler and easier to do so.
Reverse engineers, for example, can use Frida to identify hooks being used to protect or obfuscate an app. They can then test that protection, intercepting function calls and modifying or augmenting their behavior to gain deeper insights into the app's functionality,
Dynamic analysis is another approach that allows security researchers to monitor an application’s behavior in realtime. You can use a tool like Frida or debugging frameworks to intercept function calls, inspect memory, and observe network traffic for potential vulnerabilities or suspicious activity.
How You Can Use Frida to Find Hooks
For those interested in learning more about Frida and a use case for using the tool to identify hooked functions and speed up the analysis of Android applications, check out our article “Using Frida to Find Hooks.”