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What Is Code Hardening & How Does It Protect Your Code?

by Chris Brook on Thursday May 9, 2024

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Code hardening secures a system by minimizing vulnerability points where unauthorized access may occur, safeguarding data entry and extraction points.

Code hardening involves adding layers of code security to strengthen it against any potential attacks. It makes the code more resilient and difficult to exploit, for example, by using code obfuscation or encryption to protect sensitive parts of the code or by including measures to detect and prevent common vulnerabilities such as buffer overflows, injection attacks, etc. 


However, to be successful, these methods often overlap and are used in conjunction with each other to provide a multifaceted defense and strengthen the overall security of the code.


Code hardening can thwart cyber attacks by increasing the time, resources, and technical proficiency required for attackers to compromise an application.

What Is Code Hardening?

Code hardening is the process of making software code more difficult to understand, analyze, or tamper with. This is achieved through various techniques, all aiming to increase the security and integrity of the code without affecting its functionality.


Here's a breakdown of key aspects of code hardening:


Target: Primarily used for mobile applications and software development kits (SDKs), but can also be applied to other codebases.

Goal: Discourage reverse engineering attempts by making it harder for attackers to understand the code's logic and potentially exploit vulnerabilities.

Techniques: Employs various methods like:

  • Obfuscation: Renaming variables and functions with meaningless names, making the code less readable.
  • Control flow obfuscation: Altering the order or structure of the code making it harder to follow the execution flow.
  • Data encryption: Encrypting sensitive data within the code to prevent unauthorized access.

Overall, code hardening is a valuable security measure to add an extra layer of protection, especially for critical applications.

Passive Hardening

In code hardening, passive hardening is a specific approach that focuses on making the code more resistant to static analysis. This means it aims to deter attackers who try to understand the code's functionality by examining it without running it.

Here's a deeper look at passive hardening:

  • Target: Primarily focuses on decompilation, which is the process of converting machine code back into a human-readable format (like assembly language or pseudocode). Passive hardening makes decompiled code difficult to interpret and understand, making it harder for attackers to grasp the code's logic and identify potential vulnerabilities.
  • Techniques: Mainly relies on obfuscation techniques like:
    • Renaming: Changing variable and function names to meaningless or nonsensical terms.
    • String encryption: Encoding strings within the code to make them unreadable without decryption.
    • Control flow alteration: Rearranging the order of code execution or introducing redundant operations to obscure the actual logic flow.
  • Impact: Passive hardening doesn't alter the functionality of the code itself. The application still behaves the same way, but its internal workings become significantly harder to decipher.

Active Hardening

In contrast to passive hardening, active hardening in code hardening is a more dynamic approach focused on detecting and responding to attempts to tamper with or analyze the code at runtime. This means it actively monitors the application's execution environment and takes specific actions if it identifies suspicious behavior.

Here's a breakdown of active hardening:

  • Target: Primarily targets dynamic analysis attempts, where attackers run the application in a controlled environment and use tools like debuggers to examine its behavior and identify vulnerabilities.
  • Techniques: Employs various methods like:
    • Anti-debugging: Detects the presence of debuggers attached to the application and may take actions like terminating the application or altering its behavior to hinder analysis.
    • Anti-tampering: Checks the integrity of critical code sections and data to identify potential modifications or manipulations.
    • Jailbreak/rootkit detection: Identifies if the application is running on a compromised device with elevated privileges, potentially indicating increased security risks.
    • Code execution monitoring: Tracks how the code is executed and identifies suspicious patterns that might suggest tampering attempts.
  • Impact: Active hardening can modify the application's behavior in response to detected threats. This might involve limiting functionality, sending alerts, or even shutting down the application completely.

How Does Code Hardening Work?

Code hardening works by examining software and identifying potential security weaknesses. Once these weak areas are found, measures are taken to strengthen the code against vulnerabilities. 


Here’s an overview of how code hardening works:

  • Analyzing Code: The first step in code hardening involves analyzing the code to spot potential weaknesses. This may include code reviews, static analysis using software tools, or even automated scripts to comb through the code.
  • Identifying Vulnerabilities: After review, any potential vulnerabilities are highlighted. These might include parts of the code that are susceptible to known attacks like buffer overflows, SQL injection, cross-site scripting, etc.
  • Applying Fixes: Once vulnerabilities are identified, strategies are drawn up to address them. This can involve rewriting portions of the code, removing unnecessary code, or applying a patch.
  • Obfuscation: This is a technique used to make the code difficult to read and comprehend. Hackers have a harder time understanding what the code does by changing variable names to nonsense strings, rearranging code structure, or replacing straightforward code with more complex equivalents.
  • Encryption: Code encryption can be used to protect sensitive data or parts of the code. This means that even if an attacker gains access to this code, they won't be able to understand it without the decryption key.
  • Regular Updates: Code hardening is not a one-time process. Regular updates and patches are necessary to protect the code from newly identified threats.
  • Testing: Finally, the hardened code must be tested to ensure that it performs its intended function properly and that the hardening measures have not introduced new vulnerabilities.

By following these steps, developers can reduce the potential attack surface of their application, making it harder for attackers to exploit.

What Are Code Hardening Essentials?

Code hardening essentials refer to key practices and techniques utilized to protect the source code from potential data vulnerabilities and threats. Here are some of the main elements:

  • Input Validation: All input data should be validated to avoid malicious code entering the system.
  • Buffer Overflow Protection: Protecting against buffer overflow can prevent malicious code execution.
  • Secure System Calls: Ensuring any calls made to the system are secure can prevent unauthorized access or modification.
  • Securing Pointer Use: Unsafe pointer use can create vulnerabilities; therefore ensuring the safe use of pointers is essential.
  • Regular Code Audits: Regular checks on a codebase help to spot potential vulnerabilities and rectify them.
  • Use of Modern Programming Features: Modern languages and features often have built-in data protections against common vulnerabilities.
  • Updating and Patching Libraries: Ensuring all third-party libraries and software dependencies are up-to-date can prevent potential exploits.
  • Training and Education: Ensuring your team is aware of common vulnerabilities and best practices in secure coding can help prevent potential threats.

What Are the Applications Needed for Code Hardening?

There are several applications and tools utilized in the process of code hardening. These include:

  • Static Code Analysis Tools: These tools examine code without executing it and are used to identify potential vulnerabilities. Examples include SonarQube and Veracode.
  • Dynamic Analysis Tools: These tools analyze code during its execution and find bugs that static analysis may miss. Examples include Parasoft and Microfocus Fortify.
  • Security Libraries: These provide hardened features and functions to the developers to reduce the chances of introducing vulnerabilities. Examples include OpenSSL and Microsoft’s Security Development Lifecycle (SDL) cryptographic recommendations.
  • Code Signing Tools: These tools enable developers to sign their code, which verifies its authenticity and ensures third parties have not modified it. Examples include Microsoft SignTool and Jarsigner for Java applications.
  • Secure Software Frameworks: Frameworks like OWASP's Enterprise Security API (ESAPI) can provide a secure foundation for application development.
  • Automated Hardening Tools: These tools often combine several approaches, automatically applying techniques like obfuscation, shielding and encrypting, and OS-level hardening and minimizing system calls. Examples include IAST (Interactive Application Security Testing) tools like Contrast Security and Immunio.

Remember, code hardening is a concept and technique rather than a specific application or tool, so the exact methods and tools used can vary greatly depending on the specific programming language, platform, and security requirements of the project.

What are the Techniques used in Code Hardening?

Code hardening techniques aim to increase the security and resilience of software code. Here are some common strategies:

  • Input Validation: This technique involves validating the data input into a system to prevent injections, cross-site scripting, and buffer overflow attacks.
  • Principle of Least Privilege: This principle ensures that every module (like a process, a user, or a program) has the least privileges needed to perform the specific task, minimizing the potential damage if the module is compromised.
  • Secure Coding Practices: This involves following established coding guidelines to avoid known security pitfalls, such as using secure libraries or avoiding insecure functions.
  • Static Analysis Tools: These tools automatically scan source code to detect potential security vulnerabilities like buffer overflows and null pointer de-referencing.
  • Dynamic Analysis Tools: This involves analyzing an application while it’s running to detect issues that were not identified during static analysis.
  • Sandboxing: This technique restricts the capabilities of an application according to its expected behavior, which can isolate the application and limit the damage it can do if it gets compromised.
  • Privilege Separation: This involves separating a program into parts limited to the specific privileges required to perform a particular task. This limits the scope of potential damage.
  • Patch Management: Regularly updating and patching software can protect against known vulnerabilities that the software’s developers have addressed. 

Discover How Digital Guardian Can Help Protect Your Source Code

While code hardening is admirable, it does not guarantee full protection against security threats. Rather, it is an important step towards building secure software.


Digital Guardian understands how these techniques can be used together to create a layered defense, significantly reducing the likelihood and potential impact of successful attacks on your software. 

Schedule a demo today to learn how our expertise in data loss prevention, data governance, and a host of other technologies can help organizations with their code hardening.

Tags:  Source Code Security

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