External Vulnerability Scans

PCI DSS requires you to run external vulnerability scans at least once every three months using a PCI SSC Approved Scanning Vendor (ASV), remediate identified vulnerabilities until the ASV’s “passing scan” criteria are met, and perform rescans as needed to confirm fixes. Operationally, this is a recurring program: defined scope, scheduled ASV scans, tight remediation workflow, and auditable evidence. ¹

Key takeaways:

• Use an ASV and scan at least once every three months; internal tools alone do not satisfy this requirement. ¹
• You are not “done” until you have a passing ASV scan result and evidence that vulnerabilities were resolved and verified by rescans. ¹
• Most failures are operational: wrong scope, missed cadence, unmanaged exceptions, and weak ticket-to-fix evidence.

External vulnerability scanning is one of the most exam-tested PCI DSS controls because it is measurable: dates, scope, vendor qualification, and “pass/fail” outcomes are easy for an assessor to validate. Requirement 11.3.2 focuses on the part of your attack surface that an external adversary can see: public IPs, internet-facing domains, and exposed services that could provide a foothold into systems connected to the cardholder data environment (CDE) or that can impact its security.

For a CCO or GRC lead, the fastest path to operationalizing this requirement is to treat it like a compliance production line. Define the in-scope external attack surface, hire or confirm an ASV relationship, schedule scans on a recurring cadence, and run a disciplined remediation workflow that ends only when the ASV issues a passing scan. Then make the evidence retrievable on demand: scan reports, remediation tickets, approvals, and rescan results linked to closure.

This page gives you requirement-level implementation guidance you can hand to Security Operations and still defend during PCI DSS scoping and assessment. ¹

Regulatory text

PCI DSS states: “External vulnerability scans are performed as follows: at least once every three months, by a PCI SSC Approved Scanning Vendor (ASV), vulnerabilities are resolved and ASV Program Guide requirements for a passing scan are met, and rescans are performed as needed to confirm that vulnerabilities are resolved.” ¹

Operator translation: you must (1) run external scans on a defined cadence of at least once every three months, (2) run them through an ASV (not a generic scanner), (3) fix what the ASV finds until you meet passing criteria, and (4) rescan until the ASV verifies remediation with a passing result. ¹

Plain-English interpretation (what the requirement “means” in practice)

• Quarterly cadence is the floor, not the goal. If you miss a scan window or change your internet-facing footprint materially, your evidence will look stale during assessment. The text requires “at least once every three months.” ¹
• ASV is non-negotiable for this control. You can (and should) run other scanners for continuous visibility, but 11.3.2 specifically calls for a PCI SSC Approved Scanning Vendor. ¹
• Passing matters more than running. Many teams scan on schedule but never close the loop to a passing report. The requirement explicitly ties compliance to resolving vulnerabilities and meeting “passing scan” requirements, with rescans as needed. ¹

Who it applies to

Entity types: merchants, service providers, and payment processors that store, process, or transmit account data, plus service providers whose people, processes, or systems can affect the security of the CDE. ¹

Operational context (what typically falls in scope):

• Internet-facing systems that are part of the CDE.
• Internet-facing systems connected to, or that can impact the security of, the CDE (for example, jump hosts, VPN concentrators, identity services, or externally accessible admin portals that could provide a path toward CDE compromise).
• Public IP ranges and external-facing domains you control, including cloud-hosted assets.

Your assessor will expect a defensible, documented scope that maps scan targets to your PCI scope and attack surface inventory.

What you actually need to do (step-by-step)

1) Define and approve scan scope (attack surface baseline)

1. Inventory all internet-facing endpoints tied to your organization (public IPs, domains, key subdomains, externally reachable services).
2. Mark which endpoints are in PCI scope (CDE or connected-to-CDE systems) and which are out of scope, with justification.
3. Create an “External Scan Target List” that your ASV will scan each cycle.
4. Establish ownership for each target (system owner + remediation owner). Without ownership, vulnerabilities age out without closure.

Deliverable: a scoped target list approved by Security and GRC, aligned to PCI scoping.

2) Select/validate a PCI SSC Approved Scanning Vendor (ASV)

1. Confirm the provider is an ASV (document the ASV identification/validation).
2. Contract for quarterly scanning and rescans tied to passing results, not “one and done.”
3. Align on authentication and whitelisting needs (some environments require allowlisting ASV scanner IPs or scheduling windows to avoid WAF blocks).

Deliverable: ASV engagement record plus operational runbook for scan execution.

3) Schedule and run scans on the required cadence

1. Set recurring scan windows with system owners and Network/Cloud teams.
2. Run the ASV scan against the approved target list.
3. Triage results immediately into: false positives to dispute, accepted risk (if permitted by your governance), and true positives to remediate.
4. Open remediation tickets for all true positives, linked back to the scan finding ID.

Deliverable: dated scan report and a traceable vulnerability queue.

4) Remediate to “passing scan” and rescan until verified

1. Fix vulnerabilities (patch, config hardening, service removal, compensating control if appropriate and accepted).
2. Collect closure evidence while engineers work (change records, config diffs, patch confirmation, screenshots, command output).
3. Request ASV rescans as needed until the ASV’s passing requirements are met.
4. Store the passing scan report and link it to the remediation work items.

Deliverable: passing ASV scan report plus ticket closure evidence that proves vulnerabilities were resolved and verified by rescans. ¹

5) Operationalize as a control (so it survives staff and tooling changes)

1. Write a short procedure: scope management, cadence, roles, remediation SLAs (your choice), dispute handling, evidence retention.
2. Add a change trigger: any time you add a new internet-facing endpoint, update the target list and scan schedule.
3. Create a monthly control check: confirm next scan is scheduled, validate target list matches current internet footprint, and confirm no “stuck” findings.

Practical tool note: teams often track this in GRC plus ticketing plus ASV portal. Daydream can act as the control system of record by mapping scan cycles to scoped assets, attaching ASV reports, and linking remediation tickets and approvals so assessors can follow the chain without manual chasing.

Required evidence and artifacts to retain

Assessors want a clean line from requirement → scope → execution → remediation → passing result. Retain:

• External Scan Target List (with dates and approval history).
• ASV proof/attestation that the scanning party is a PCI SSC Approved Scanning Vendor.
• Quarterly ASV scan reports (including failed scans, not only passing).
• Passing scan reports that demonstrate ASV Program Guide passing criteria were met. ¹
• Rescan records showing verification after fixes. ¹
• Remediation tickets tied to findings (ticket IDs referenced in scan response notes if possible).
• Change management evidence: patch deployment records, configuration changes, exception approvals where applicable.
• False positive disputes: evidence submitted and ASV acceptance/closure.

If you cannot produce these quickly, you will spend assessment time reconstructing history. That reconstruction often exposes missed scans or incomplete remediation trails.

Common exam/audit questions and hangups

Use these as a readiness checklist:

• “Show me the last four quarters of external ASV scans and the passing results.” ¹
• “How do you prove scans occurred at least once every three months?” ¹
• “What is your scope? How do you know these IPs/domains are complete?”
• “When a scan fails, who owns remediation and how do you track it to closure?”
• “Show me an example where you remediated, rescanned, and obtained a passing result.” ¹
• “How do you handle new external assets introduced mid-quarter?”

Frequent implementation mistakes (and how to avoid them)

1. Scanning the wrong things (or missing things). Fix: maintain a living target list tied to your external inventory and cloud account subscriptions; require review during release/change processes.
2. Assuming internal scanners satisfy 11.3.2. Fix: run internal tools for continuous coverage, but ensure quarterly evidence comes from an ASV. ¹
3. Treating a failed scan report as “evidence.” Fix: keep failed reports, but drive to a passing scan and document remediation and rescans. ¹
4. No rescan discipline. Fix: make “ticket cannot close without rescan verification” the rule for externally found vulnerabilities.
5. False positive chaos. Fix: define a dispute workflow with required proof (configuration outputs, version evidence) and keep the ASV’s closure response.
6. WAF or rate-limiting blocks the scan, then everyone moves on. Fix: pre-coordinate allowlisting and schedule; treat scan failure as an incident for compliance purposes until resolved.

Enforcement context and risk implications (practical, not speculative)

No public enforcement cases were provided in the source catalog for this specific requirement, so this page does not cite specific penalties or case outcomes.

Operationally, the risk is straightforward: if you do not scan on a defined cadence, externally exploitable weaknesses can remain exposed, and you will have incomplete remediation evidence during PCI scoping, assessor testing, and follow-up. ¹

Practical execution plan (30/60/90-day)

The requirement is time-bound (“at least once every three months”), so focus on establishing a repeatable cycle and clean evidence. ¹

First 30 days (stabilize scope + ASV readiness)

• Establish your External Scan Target List and get it approved.
• Confirm ASV engagement and scanning logistics (windows, allowlists, contacts).
• Define ticketing fields required for traceability (finding ID, asset, remediation owner, target rescan date).
• Run an initial baseline ASV scan if you do not have a recent one, then start remediation immediately.

Days 31–60 (drive to passing + evidence quality)

• Work the remediation backlog with weekly triage.
• Dispute false positives with documented proof.
• Request rescans quickly after fixes; do not batch everything to the end.
• Build an “assessment pack” folder: scan reports, passing proof, ticket exports, approvals.

Days 61–90 (make it repeatable)

• Add scope-change triggers (new internet-facing assets must be added to scan targets).
• Add a control owner review cadence: confirm next scan scheduled; verify previous quarter is fully passing with evidence.
• Automate evidence collection where possible (GRC record + ASV report attachments + ticket links). Daydream is a practical fit if you need one place to assemble scan cycles, scope approvals, and remediation evidence for assessors.

Frequently Asked Questions

Do we have to use a PCI SSC Approved Scanning Vendor (ASV), or can our internal scanner count?

Requirement 11.3.2 explicitly requires scanning “by a PCI SSC Approved Scanning Vendor (ASV).” Internal scanning is still valuable, but it does not replace the ASV evidence for this requirement. ¹

What does “at least once every three months” mean operationally?

Treat it as a recurring maximum gap between scans, not “quarterly-ish.” Set a schedule you can consistently meet and retain dated reports to show no interval exceeds the requirement. ¹

If we fail an ASV scan, are we automatically noncompliant?

A failed scan indicates open vulnerabilities and incomplete fulfillment of the requirement’s “passing scan” expectation. Keep the failed report, remediate, and perform rescans until you achieve a passing scan. ¹

Do we need to rescan after every fix?

The requirement states that “rescans are performed as needed to confirm that vulnerabilities are resolved.” In practice, rescan whenever remediation is claimed complete for findings that affected the pass result. ¹

What evidence is most persuasive to an assessor?

A passing ASV scan report plus tickets that show each finding was tracked, fixed through change control, and verified by rescan. Assessors look for traceability from finding to closure, not screenshots alone. ¹

How do we handle new internet-facing assets created between quarterly scans?

Update the scan target list through a change trigger and coordinate an ASV scan for the new endpoint rather than waiting for the next scheduled cycle. Keep the updated scope approval and scan report as evidence of control operation.

What you actually need to do

Use the cited implementation guidance when translating the requirement into day-to-day operating steps. ²

Footnotes

1. PCI DSS v4.0.1 Requirement 11.3.2

2. Just Published: PCI DSS v4.0.1