9 Secure Code Review Best Practices For Your Web Application

Modern web applications are feature-rich to provide a seamless user experience and intuitive flow through business data and logic.

Due to rising customer demands and rapid, feature-driven development, security often takes the backseat and vulnerabilities are introduced and oftentimes go undetected.

A secure code review helps identify these security vulnerabilities and weaknesses that might go undetected otherwise. It applies a set of security standards to the code to ensure secure coding best practices and development have been followed.

Secure code reviews use automated tools, checklists, thread modeling, software development experience, and security experience to identify security vulnerabilities can be mitigated.

9 Secure Code Review Best Practices

Secure code reviews should be ingrained as part of the Software Development Life Cycle (SDLC).

Here are some of the most effective secure code review best practices that you should follow:

1. Create a Comprehensive Secure Code Review Checklist

Each software solution has its own security requirements and features so a code review can vary from one software application to another.

Having a comprehensive secure code review checklist helps ensure that you don’t miss key items and perform a thorough code review.

Here are some questions you should consider while conducting a secure code review:

  • Have you implemented proper authorization controls?
  • Have you implemented proper authentication controls? Do you have two-factor or multi-factor authentication in place?
  • Is sensitive data encrypted? How do you handle encryption keys?
  • Does the error message display sensitive information to the user?
  • Do you have other security controls in place that prevent SQL Injection, XSS attacks, malware, etc?

These are just a few questions that you might want to include in your secure code review checklist. Keep in mind that a checklist might not be exhaustive in many cases, but it can provide a direction to the code reviewer and help them perform effective secure code reviews and deliver high-quality and secure code.

2. Review Constantly

It is essential for companies to perform secure code reviews regularly to ensure that whenever a significant change is made into the code, it is effectively reviewed.

A secure code review doesn’t need you to wait for the development process to be completed. Rather you can perform a code review as the development progresses.

By reviewing your code regularly, you can identify loopholes or loose ends that could be exploited by attackers and fix them in a timely manner. It also enhances the overall security of the code and results in higher quality code, making future implementations quick, easy, and affordable.

3. Use Threat Modeling

Threat modeling enables organizations to identify threats and develop efficient responses. Having a structured threat modeling process in place helps to detect, understand, and communicate threats and mitigations to protect the application assets.

Threat modeling can take place during planning, design, development and/or later deployment phases. It not only helps identify risks but also helps teams to better understand the relationship between an application’s various components.

As the application’s environment and design changes throughout the project’s life, having the knowledge of how the components are interconnected with the product is valuable. This can help you understand the security threats and risks better.

4. Use Automation Tools to Save Time (But Don’t Let Automation do EVERYTHING)

Automation tools can play a crucial role, especially in securing software as the code you have, the less effective your code review might be at detecting code flaws line by line.

With applications consisting of hundreds of thousands, if not millions, of lines of code, it’s impossible to perform a comprehensive code review line by line manually in any reasonable amount of time.

Automation tools enable streamlined processes with minimal human intervention allowing them to focus on more complex tasks that require logical or business analysis. Automated static code analysis tools provide nearly full code coverage along with the ability to reveal vulnerabilities that might otherwise go undetected if checked manually.

For instance, if a static code analysis tool discovers an SQL or an XSS injection vulnerability, it could result in searching the codebase for similar vulnerable patterns, a time-consuming and practically impossible task if done by hand.

While you can rely on automation for many things, you can not rely on it for everything. Despite the fact that automation offers numerous benefits, it also poses certain challenges, for example, automation can’t find design and architectural flaws among many other flaws that automation cannot reliably detect.

Since automation tools do not have a proper understanding of business processes, they are unable to find flaws in logic areas. In addition to this, automation also creates a lot of false positives, which can derail the entire testing process since reviewers have to then check these identified vulnerabilities manually.

5. Use the Expertise of an Application Security Professional

While automated tools are more efficient than their human counterparts in performing time-intensive tasks such as searching for vulnerable code patterns within a massive codebase, they fall short in a variety of other aspects.

This is why an application security professional is needed to bind together the secure code review process and provide clarity and context to it. The experience and knowledge of a security analyst or code reviewer is indispensable in the secure code review of a web application. For example, in tasks where the code review needs their ability to identify application logic issues.

However, you can leverage the strengths of security professionals and those of automated tools to advance your secure code review process, allowing security teams to determine a comprehensive array of risks and vulnerabilities.

6. Validate Your Input and Output

A major part of a secure code review is to analyze the attack surface of the software. Attackers often use input and output to exploit vulnerabilities of an application and gain access to information or conduct other malicious activities.

The primary goal is to identify and review various inputs from all untrusted data sources and validate outputs as well. By validating the input, you can ensure that your application handles the untrusted input appropriately so that potentially malicious input is not used to attack the application..

By validating output, you can ensure that your application doesn’t harm the end user or other systems that ingest data from your application.

Inputs may come from the cookies, data feeds, service responses, command lines, flat files, property files, environment variables, external processes, and the browser. Check the valid semantics and syntax of information system inputs (such as character length, set, acceptable values, and numerical range) to ensure that inputs match specified standards for content and format.

Input validation helps ensure accurate inputs and prevent attacks such as SQL injection, cross-site scripting, and a wide range of other injection attacks. Therefore, it is critical that applications validate input data before they process it.

Additionally, when you are sending output data to a user’s web browser, a network, a file, or some other place, you need to ensure that the data you send is safe.

7. Enforce Least Privilege

Another secure code best practices include the implementation of least privilege model that allows authorized users to specifically access only information that they need to perform their job functions or tasks. For instance, a user account responsible to maintain the customer records does not need access to other employees’ financial records.

Surprisingly, the 2019 Global Data Risk Report revealed that over 22% of folders were open to every employee. These folders may contain sensitive data, and a malicious insider actor may use these folders to conduct data breaches in their organization. Therefore, it is highly crucial to implement the least privilege access model.

In some instances, if a user needs admin rights or higher privileges to access a specific data, it must be provided for only the minimum time required to complete the task. The least privilege model significantly reduces the scope of harm that can be caused by the unauthorized or unwanted use of network privileges.

8. Conduct Secure Application Development Training

As more data breaches occur, cybersecurity professionals try to stay abreast of the latest technology and tools to ensure a secure application or system. But it’s not just the security team that should be responsible for maintaining security in your software.

Conduct regular training sessions on secure application development to educate your developers about secure coding, and how they can use it to improve software development processes while reducing code vulnerabilities.

Secure application development will help identify and mitigate risks early in the development process which will further reduce the possibility of data breaches and cyberattacks.

9. Manage Your Vulnerabilities

A secure code review might reveal an array of security risks and vulnerabilities. It is important to identify, evaluate, mitigate, and report these security vulnerabilities in the system and the software that runs on them.

Managing your vulnerabilities is critical for organizations to prioritize potential threats and minimize their attack surface.

Some scanning tools also include vulnerability remediation which categorizes and ranks the vulnerability according to their risk and severity. This is often done by comparing the vulnerabilities against security policies.

With every change in the application comes the risk of a potential loophole being opened in your software that could be exploited by attackers. This might impact your company’s market reputation and credibility.

Final Thoughts

A secure code review is a time-intensive process that can be performed efficiently using both the strengths of automated tools and the expertise of security professionals.

A secure code review often reveals many insights into the code. Apart from finding new security risks or learning new techniques, you can also check how your development team approaches coding. Better practices can be adopted to conduct a more precise and effective code review.

If you have any questions about these secure code review best practices or need any help with your secure code review, please contact us.


Cypress Data Defense was founded in 2013 and is headquartered in Denver, Colorado with offices across the United States. Our goal is to help organizations secure their IT development and operations using a pragmatic, risk-based approach. The diverse background of our founders allows us to apply security controls to governance, networks, and applications across the enterprise.

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