Quarterly vulnerability scans are required by PCI DSS to protect cardholder data and keep networks secure.

Vulnerability scans aren’t just a checkbox on a compliance form. Think of them as a regular health check for the systems that handle card data. They help you spot weaknesses before a bad actor does, and they’re baked into the way PCI DSS expects organizations to protect cardholder information. So, how often should these internal and external scans happen? The short answer is: quarterly. Let me unpack why that cadence makes sense and what it looks like in practice.

The quarterly rhythm: why every three months matters

If you’ve ever watched a weather forecast, you know forecasts aren’t perfect, but they’re still useful. The quarterly scan cadence is similar. Threat actors constantly search for new footholds—unpatched software, misconfigured devices, exposed services. The environment you’re protecting isn’t static; it changes with new deployments, patches, configuration tweaks, and additions. Scan too rarely, and you risk letting newly introduced vulnerabilities linger long enough to be exploited. Scan too often without a clear remediation plan, and you might burn through resources chasing every tiny finding. The quarterly interval hits a practical balance: frequent enough to catch fresh issues, but measured enough to manage remediation realistically.

Here’s the thing about PCI DSS: it expects you to stay vigilant even as you evolve. Quarterly vulnerability scans give you a predictable, repeatable process to identify weaknesses that could enable attackers to reach cardholder data. When combined with timely remediation, they form a defense in depth that’s hard to bypass.

Two sides of the coin: internal and external scans

Let’s keep the picture concrete. PCI DSS calls for both internal and external vulnerability scanning, and both have the same quarterly cadence, though they cover different landscapes.

• Internal vulnerability scans: These look inward, at the networks and systems inside your boundaries. You’re scanning behind the firewall, behind segmentation controls, and across servers, workstations, and applications. The emphasis is on authenticated and credentialed scans that can reveal misconfigurations, missing patches, weak service configurations, and flawed access controls. The internal scan helps you see what a ready-made attacker who’s already inside your perimeter might spot.

• External vulnerability scans: These zero in on what’s exposed to the outside world—your public-facing assets, such as web servers, APIs, and cloud endpoints. No wall behind the exterior network shields these from the wider internet, so external scans help you understand what an outside observer could discover. They’re crucial for identifying open ports, misrouted services, or unpatched internet-facing software.

The common thread is the quarterly cadence, but the targets are different. Together they give you a fuller picture of where risk lives, both on your internal corridors and on the front porch where curious passersby might notice you.

What counts as “quarterly” in the real world

The quarterly requirement isn’t a one-and-done date on a calendar. It’s a rolling process with incentives to stay current. Here’s how it typically plays out in practice:

• Schedule: You set scans to run at least once every 90 days. Many teams choose a fixed quarterly window—say, the first full week of January, April, July, and October—to keep things predictable.

• After changes: If you implement significant changes—new network segments, major app updates, new remote access services, or a big cloud deployment—you should re-scan promptly after those changes. The idea is to catch new vulnerabilities introduced by changes before they become problems.

• After remediation: When a vulnerability is found, you don’t just note it and move on. You remediate it and verify that the remediation was effective via a follow-up scan. Document the results so you can show progress over time.

• Scope clarity: Make sure all assets within scope for PCI DSS receive the quarterly scan. It’s easy to miss a nonstandard server, a development or staging environment that’s reachable from the inside, or a cloud instance that was overlooked. A good asset inventory makes quarterly scanning feasible and reliable.

A gentle note on the frequency

Some people wonder if monthly scans would be better. The answer is nuanced. Monthly scanning can be valuable in highly dynamic environments or in the midst of a critical change window, but it can also strain teams if remediation isn’t aligned with the scan cadence. The PCI DSS standard emphasizes regular checks—quarterly—and requires additional scans when changes occur. Monthly might be overkill for many shops, while annual scans clearly fall short of the standard. Quarterly is a practical middle ground that keeps risk in view without burning out resources.

Remediation, evidence, and the bigger picture

Scanning is only one part of the story. The goal is to discover, assess, and remediate vulnerabilities—fast enough to reduce risk while keeping business operations smooth. In a PCI DSS context, you’ll typically need to gather and maintain evidence:

• Scan results: Logs, reports, and findings from the internal and external scanners.

• Vulnerability details: Severity ratings, affected assets, and specific weaknesses.

• Remediation steps: What you changed, when you fixed it, and who verified the fix.

• Verification scans: Post-remediation scans to confirm the vulnerability is addressed.

• Change context: Any changes in the environment that could affect risk, such as new devices, services, or network configurations.

This is more than a compliance checkbox—the evidence you keep helps you communicate risk to leadership and demonstrates a structured approach to protecting cardholder data.

Tools and practicalities you’ll encounter

If you’re digging into how these scans operate in the field, you’ll likely meet a few familiar names and concepts:

• Tools: Qualys, Nessus, Rapid7, and similar platforms are common choices for both internal and external scanning. Many organizations run multiple tools to cross-check findings and maintain coverage across diverse tech stacks.

• Authenticated vs. unauthenticated scans: Internal scans often use credentials to access more depth (authenticated). External scans typically don’t require credentials, but some assessments can include authenticated external scans if appropriately scoped.

• Remediation workflows: It’s not enough to log a vulnerability; you need a process to assign, track, and verify fixes. That includes prioritizing remediation by risk level and impact on cardholder data.

• Cloud and virtualization: Modern environments aren’t just a pile of on-prem servers. Pods, containers, and cloud instances add complexity to asset inventories, which makes your quarterly cadence even more important—and a bit more challenging.

Common pitfalls to watch for

As you study these topics, you’ll hear about teams that stumble on the cadence or the coverage. Here are a few pitfalls that come up frequently, so you can avoid them in real life:

• Skipping after changes: If you deploy a patch or introduce a new service and skip the follow-up scan, you’re banking on time-to-exploit being slow. Don’t bank on luck.

• Missing assets: An overlooked server or a misconfigured network device can hide under the radar. Start with a robust asset inventory to ensure every piece of relevant infrastructure is in scope.

• Poor remediation visibility: If teams fix vulnerabilities but don’t document what was changed and when, auditors won’t see the progress. Clear, testable evidence matters.

• Overemphasis on “finding”: Scans reveal a lot of noisy data. The real value comes from triaging findings, prioritizing fixes, and verifying remediation.

How to make the cadence work for you

Here are a few practical ideas to keep quarterly scans effective, affordable, and not a burden:

• Automate scheduling: Use calendar-based automation so scans run predictably and you don’t have to chase reminders.

• Integrate with change management: Tie scanning into your change approval process. When you sign off on a major deployment, trigger a scan to verify no new vulnerabilities were introduced.

• Incidentally align with patches: If you’re patching software, plan the scan right after patches go in. If you’re delaying patches, you’ll want to scan more frequently to catch the temping windows of exposure.

• Cross-team visibility: Security, IT operations, and development teams should own the process together. Clear roles clarify ownership of findings and remediation tasks.

• Build a remediation SLA: Agree on target timelines for fixing critical issues. When time matters, speed matters, but so does accuracy.

Bringing it back to the core idea

So, the right answer to the core question is quarterly. Internal and external vulnerability scans—performed on a quarterly basis—help organizations manage risk in a world where threats evolve and the landscape shifts with new technology. The cadence isn’t just a number; it’s a disciplined approach to staying ahead of weaknesses that could expose cardholder data. And when you add after-change scans, proper remediation, and solid evidence, you create a security baseline that’s meaningful, not just ceremonial.

If you’re exploring PCI DSS through the lens of a security role, you’re naturally curious about how a mature scanning program looks in reality. You’re not just checking boxes; you’re building resilience. The quarterly cadence is a cornerstone of that resilience, a steady heartbeat in an otherwise noisy environment. It’s a practical ritual that keeps risk in check without slowing business momentum.

A final thought to keep in mind

Security isn’t a single trick or a flashy tool. It’s a steady rhythm of assessment, adjustment, and verification. Quarterly vulnerability scans are the heartbeat of that rhythm for many organizations protecting card data. They’re a reminder that risk isn’t a one-time event but a continuous journey—one that rewards consistency, proper coverage, and relentless attention to detail.

If you’re mapping out how this all fits into real-world work, imagine this: you have a security program that treats every 90 days as a fresh checkpoint, a moment to re-evaluate your exposure, adjust defenses, and show progress. That’s the essence of PCI DSS coverage in action—practical, approachable, and built for the long haul. And yes, quarterly is the cadence that keeps it honest.