Understanding PCI DSS Requirement 6: Secure Development and Maintenance of Systems and Applications

What Requirement 6 really asks for in PCI DSS

Let’s start with a simple truth: PCI DSS isn’t just about locks on data centers. It’s about building secure software from the ground up. When people ask what Requirement 6 covers, the answer is straightforward—and a little planning-heavy. Requirement 6 is all about the development and ongoing maintenance of secure systems and applications. In plain terms: security has to be baked into the software development lifecycle, not slapped on after the fact.

Here’s the thing: security isn’t a one-time scarab that you stamp on a product at the end of a long journey. It’s a discipline you carry with you from the first lines of code to the last patch. That mindset—security by design—pays off in fewer flaws, faster risk responses, and a healthier tech ecosystem for everyone who touches the system, from developers to operators to customers.

What Requirement 6 entails, in practical terms

• Start with security requirements up front. Before a single line of code is written, teams should identify what security needs exist for the software and the environments where it runs. This means risk assessments, threat modeling, and a plan that ties security to the product’s purpose and data sensitivity.

• Build security into the SDLC. Secure development isn’t an afterthought. It’s integrated into the software development lifecycle. That means secure coding guidelines, regular design reviews, and automated checks that run as part of the build and deployment processes.

• Use secure coding practices. Developers should follow established guidelines that reduce common vulnerabilities. Think things like input validation, proper error handling, parameterized queries, and safe session management. It sounds basic, but it’s the difference between a feature that works and a feature that can be exploited.

• Review and test changes continuously. Every change deserves scrutiny. Code reviews, peer validation, and security testing should be routine, not rare. When teams test early and often, you catch flaws before they become brittle, expensive fixes.

• Manage changes with care. A robust change management process keeps track of modifications, who approved them, and how they’re tested. This isn’t bureaucracy for bureaucracy’s sake—it's a shield against introducing new vulnerabilities when you update software or infrastructure.

• Patch and update as a continuous loop. Vulnerabilities don’t announce themselves with a calendar. When a flaw is found—whether in your own code or in a library you depend on—you’ve got to respond quickly, with tested fixes and a clear deployment plan.

• Verify security through testing. Security tests aren’t a one-off ritual. They’re an ongoing practice: static code analysis, dynamic testing, and ongoing assessments of dependencies. It’s also smart to re-check after patches, changes, or feature additions to confirm that nothing regressed.

• Coordinate across teams. Security can’t live in a single silo. Developers, security engineers, operations, and the business side need shared language and processes. In practice, that means shared risk registers, transparent remediation timelines, and clear ownership of security tasks.

A relatable way to picture it

Think of Requirement 6 like building a house with a security-minded blueprint. You don’t set up the alarm system after the doors are hung. You draft it into the plan, pick materials with safety in mind, and schedule regular inspections as the house ages. The same logic applies to software: you design with protections, build them in, and keep checking them as the software evolves.

The “other options” that aren’t the core focus, explained

If you’re ever confronted with a multiple-choice question, you’ll notice other security activities pop up in the broader scope of an organization’s program. However, they don’t pinpoint the heart of Requirement 6:

• Regular audits of security systems (A): Audits matter, but they’re more about verification and oversight, not specifically about the secure development and maintenance of software.

• Encryption of user passwords (C): Encryption is essential for protecting credentials, but it’s typically addressed in other parts of PCI DSS (and in how you protect data in transit and at rest). It’s not the central theme of developing and maintaining secure software.

• Implementation of User Acceptance Testing (D): UAT is valuable for confirming that software meets user needs, but it isn’t the primary driver of secure development practices.

So, the right takeaway is B: Development and maintenance of secure systems and applications. The aim is to weave security so tightly into creation and upkeep that vulnerabilities become rarities rather than headlines.

Why this requirement matters beyond a checklist

Security isn’t a single control; it’s a culture. Requirement 6 nudges teams to move from “we’ll fix it later” to “security is part of every change.” When teams adopt this mindset, you see fewer patch-worthy defects, less friction during releases, and a more resilient product overall.

A few practical examples you’ll encounter in real-world work

• Threat modeling sessions at the kickoff of a project. Teams lay out “what can go wrong” and map controls to those risks. It’s not about pessimism; it’s about preparedness.

• Secure coding guidelines as the default, not the exception. These guidelines cover input handling, authentication flows, session lifetimes, and error reporting. They’re living documents updated as threats evolve.

• Automated testing that runs with every build. Static analysis catches common mistakes; dynamic analysis tests how the running app behaves under realistic conditions. Dependency scanning flags vulnerable libraries before they become a problem.

• Regular code reviews focused on security yes, but done with empathy. The goal is improvement, not blame. When teams support each other, you get cleaner code and fewer back-and-forth debates about fixes.

• A shared risk and remediation calendar. When someone discovers a vulnerability, there’s a clear path to patching, regression testing, and deployment without derailing other work.

A few tips to keep the momentum

• Start small, scale thoughtfully. Don’t try to solve every risk at once. Pick a few high-impact areas and build the habit of secure development around them.

• Invest in education that sticks. Short, hands-on workshops beat long lectures. Practical exercises build muscle memory that sticks across teams.

• Use tools that fit the workflow. Integrations with your favorite IDEs, CI/CD pipelines, and issue trackers help security checks feel like part of the job, not a detour.

• Keep the conversation human. Security isn’t just for the security team. Developers, testers, product managers, and operators all contribute. A shared language helps.

Where the philosophy meets the daily grind

Let me explain with a quick analogy. Imagine your software as a car. Requirement 6 is the discipline of making that car safe to drive, not just a flashy exterior. The brakes, the airbags, the steering—these are the secure coding practices, the threat modeling, and the ongoing testing. The service schedule and maintenance windows are your change management and patching routines. If you neglect those, your shiny new vehicle might still surprise you in the worst way when you’re on the highway. The same logic applies to software that handles cardholder data: it has to stay solid, updated, and resistant to new quirks and threats.

A nod to the tools you’ll encounter

• Static and dynamic analysis tools (think: SonarQube, Fortify, Veracode) to catch issues early in the coding cycle.

• Software composition analysis (SCA) to know what libraries and dependencies you’re pulling in and whether they have known vulnerabilities.

• Secure SDLC templates and threat modeling guides that keep security checks consistent across teams.

• Version control and code review workflows that make security doable without slowing everyone down.

Final takeaway

Requirement 6 isn’t a mere checkbox. It’s a philosophy: build secure systems and keep them secure as they change. By weaving security into every stage of development and maintenance, organizations create software that’s tougher to break, easier to improve, and better aligned with the needs of users and merchants alike. It’s about turning security into a daily habit, not a quarterly audit, and that habit pays off in trust, resilience, and smoother operations all around.

If you’re curious about how different teams implement these ideas, or you want a sense of what successful security-minded development looks like in practice, I’m happy to share more examples and stories from the field. After all, the best protection isn’t a big shield on the wall—it’s a steady rhythm you carry with you through every line of code.