Secure Software Development

Secure software development is a methodology for developing software that explicitly builds security into each phase of the software development life cycle (SDLC). From the very beginning, the best practices for secure software development require that security is planned and developed within the code at the very beginning. Security is part of the earliest part of the development cycle when the architecture is designed. The goal is to have a comprehensive, secure software development policy before a single code statement has been written. This policy should include the best practices and processes the software development team should follow to minimize the occurrence of vulnerabilities within the developed software.

Recently, we observed cyber attacks which directly impacted the software supply chain. Cyberattackers compromised the heart of the software development process by placing their malicious code into the continuous integration and continuous development (CI/CD) pipeline. Once the CI/CD pipeline is compromised, especially in a SaaS software environment, the malicious code loaded by cyber attackers will then be downloaded into hundreds or thousands of customer environments. All of this continues to raise the urgency and importance of secure software development and the best practices which support it.

The cost savings associated with fixing a software bug early in the software development cycle can be less expensive than fixing the same bug later. There are also obvious benefits to brand and reputation by reducing the likelihood of data breach events linked to poor development practices involving your software.

At the 1,000-foot view, building out secure software development is driven by “testing early and testing often.” From a design perspective, it is common for software teams to develop functional requirements. Yet so many do not create nor document security requirements. As with any protocol, you must examine the high-risk areas specific to your environment, develop a comprehensive risk analysis, and then use that in development as a guideline to help design your secure software development plan.

People are an essential part of the equation. Secure software development policies must establish the rules of engagement your people will follow in developing code. In addition, periodic reviews and testing protocols must be in place to ensure that all work meets the organization’s standards and policies. 

Well-defined processes should ideally separate critical environments. For example, access to software development should be separate from access to the test environment and the production environments. In addition, meticulous version control must be managed and enforced, and data protection rules should also be implemented at the detail level. 

A secure software development plan may be mandatory for your organization. For example, if you need to implement ISO 27001, there are resources to build out a policy from a template that is part of ISO 27001. SOC 2 Type 2 is another example of a framework requiring conformance by building a compliant secure software development environment. 

The NIST Frameworks for Secure Software Development 

Several frameworks can help you accelerate your efforts to design and implement an SSD environment. These include NIST’s Secure Software Development Framework (SSDF). The SSDF is a set of secure software development practices based on established secure software processes from organizations such as BSA, OWASP, and SAFE Code. The best practices defined within SSDF should be integrated with each SDLC implementation.

SSDF best practices will help software developers minimize or eliminate the number of vulnerabilities in software. SSDF provides a common language and taxonomy for describing secure software development practices. This common language enables software developers to rapidly adopt and utilize it within their partner and vendor ecosystems.

The SSDF includes best practices which are structured into four groups as follows:

• Preparing the organization helps ensure that the organization’s people, processes, and technology are ready to perform secure software development at the organization and group levels.
• Protecting the software helps safeguard software components from manipulation, tampering, and unauthorized access.
• Producing Well-Secured Software is about minimizing the number of vulnerabilities that may be present in a software release. 
• Respond to Vulnerabilities makes actionable responses to vulnerabilities in software releases. Response to vulnerabilities requires the organization to address those vulnerabilities and prevent similar vulnerabilities from occurring again and in the future.

Each best practice shown above is defined with the following structural elements:

• Practice includes a statement of the procedure, a unique name or identifier, and an explanation of the process and its benefits.
• Tasks are the actions required to accomplish a practice.
• Implementation examples are used to demonstrate a practice to make it more understandable.
• The reference uses a secure development practice document and maps it back to a particular task.

NIST’s SSDF are outcome-based – they can help you compare the outcomes an organization is currently achieving to the SSDF’s practices to identify gaps that must be addressed. Then a resulting action plan to mitigate these gaps can drive priorities. Of course, this must align with the organization’s business and the risk management processes it requires. 

Risk alone is not sufficient. Other variables such as cost and fit should be considered when deciding which SSDF practices to apply. On a very practical basis, allocating time and other assets must consider an organization’s resources. Automation is critical – this is required to gain both reliable repeatability and scale. 

The NIST SSDF’s practices, tasks, and implementation examples provide a good template from which to start. However, the NIST SSDF is not an inflexible checklist – SSDF is more of a baseline to begin the planning process, drive best practices, and continuously improve the security of your software development environment.

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