Build vs Buy: Deciding How to Approach DAST Scanning

Build vs Buy: Deciding How to Approach DAST Scanning

For a scaling tech company, the pressure is on to ship features and grow. Yet, as your applications become more complex and handle more sensitive data, securing your public-facing web assets is non-negotiable. This brings engineering leaders to a familiar crossroads: when it comes to Dynamic Application Security Testing (DAST), do you build your own solution or buy a commercial one?

The impulse to build is understandable. Your team has the engineering talent, and a custom-built tool seems like the perfect way to get exactly what you need. However, the decision isn’t just about initial development. It involves weighing long-term maintenance, opportunity cost, and the specialized nature of security tooling. Making the right choice about dast scanning requires a strategic look at your company’s resources, priorities, and ultimate business goals.

The Case for Building: The Dream of a Perfect-Fit Solution

Building a DAST scanner from the ground up offers the ultimate level of customization. You can tailor it to your specific technology stack, internal workflows, and unique risk tolerance. For reference, the OWASP Foundation offers a comprehensive guide on web application security testing standards and methodologies—an invaluable blueprint if you’re considering a build approach.

Pros of Building:

  • Total Customization: Your tool can be designed to do exactly what you want, without any of the features you don’t need. It can integrate seamlessly with your proprietary CI/CD pipelines and internal alerting systems.
  • No Subscription Fees: On the surface, this is a major draw for the CFO. You avoid recurring licensing costs, which can seem like a significant saving.
  • Deep In-House Knowledge: The process of building a DAST tool forces your team to develop deep expertise in web application security, which can be a valuable long-term asset.

It’s essential to recognize, however, that building such a tool isn’t just about code—it’s about keeping current with research, threat trends, and industry expertise. According to the National Institute of Standards and Technology (NIST), regular updates and adherence to latest testing procedures are critical to maintaining an effective DAST tool.

While these benefits are appealing, they come with significant and often underestimated costs.

Cons of Building:

  • Massive Opportunity Cost: This is the most critical factor. Every engineer working on an internal security tool is an engineer not working on your core, revenue-generating product. For a company that just raised a Series A or B, speed to market is everything. Diverting top talent to an internal project can slow down your growth.
  • The Never-Ending Maintenance Treadmill: A DAST scanner isn’t a one-and-done project. The web is constantly evolving, with new frameworks, attack vectors, and vulnerabilities emerging daily. Your internal tool will require a dedicated team to provide continuous updates, patch its own flaws, and maintain the complex logic needed to accurately identify real threats without drowning everyone in false positives.
  • Time to Value is Slow: A production-ready DAST tool that is both effective and reliable can take months, or even years, to build. During that entire development period, your applications remain untested and exposed to external threats.
  • Requires Niche Expertise: Effective DAST scanning requires highly specialized knowledge. It’s not just about sending HTTP requests; it’s about understanding how to crawl modern single-page applications (SPAs), manage session states, and craft payloads that uncover vulnerabilities like XSS and SQL injection without breaking the application.

The Case for Buying: Leveraging Specialization for Speed and Focus

Purchasing a commercial DAST solution allows you to outsource the complexity of security tooling to experts, enabling your team to stay focused on its primary mission. For authoritative guidance on DAST tooling and integration in application security programs, the OWASP Foundation provides a thorough overview of industry best practices. Additionally, US government resources, such as CISA’s guidance on web application security, highlight the importance of automated, up-to-date scanning tools.

Pros of Buying:

  • Immediate Time to Value: A commercial DAST tool can be implemented and running its first scan in hours or days, not months. This provides immediate visibility into your external attack surface and dramatically shortens the time it takes to reduce risk.
  • Access to Expert Knowledge: You’re not just buying software; you’re buying the ongoing research and development of a company dedicated solely to security. They are responsible for keeping up with the latest threats and ensuring the scanner is effective against modern web technologies.
  • Lower Total Cost of Ownership (TCO): When you factor in the salaries of the developers needed to build and maintain a custom tool, plus the opportunity cost of pulling them from your core product, a commercial subscription is often far more cost-effective. Predictable, per-developer pricing models are especially attractive for scaling teams.
  • Focus on Your Core Business: This is the ultimate advantage. Your engineers can focus 100% of their energy on building and improving the product that your customers pay for, which is the engine of your company’s growth.

Naturally, buying a solution has its own considerations.

Cons of Buying:

  • Recurring Subscription Costs: This is a line item in your budget that requires approval, unlike the “hidden” costs of an internal build.
  • Risk of a Poor Fit: A generic, one-size-fits-all tool might not align perfectly with your team’s workflow, potentially causing friction.
  • Vendor Dependency: You rely on the vendor for updates, support, and future feature development.

Making the Right Decision for Your Growth Stage

For most fast-growing tech companies, the strategic calculus points clearly toward buying. Your most limited resource is developer time, and it should be invested in activities that directly drive customer value and revenue.

Here’s how to frame the decision:

  1. Assess Your Core Mission: Is your company in the business of building security software? If not, it’s generally more strategic to buy from a specialist.
  2. Calculate the Real TCO: When pitching to leadership, go beyond the subscription fee. Compare it to the fully-loaded cost of building, including salaries, benefits, and the massive opportunity cost of delayed feature releases.
  3. Prioritize Speed and Security: How quickly do you need to secure your applications? If you’re preparing for a SOC 2 audit or handling sensitive customer data, you can’t afford to wait. A commercial tool delivers protection now.
  4. Look for Modern, Integrated Tools: The market for DAST tools has matured. The best solutions are no longer rigid black boxes. Look for platforms that offer seamless integration with your existing workflow, provide a single pane of glass for all your security findings, and are designed to minimize false positives, so your developers can focus on what matters.

Ultimately, choosing to buy a DAST scanner is a strategic decision to prioritize focus and speed. It allows you to protect your company effectively while keeping your engineering team aimed at its most important target: building a successful product.