Where Does PCI DSS Apply? Scope & Coverage Guide

Introduction

Where Does PCI DSS Apply? This simple question matters more than you might think. Picture your web store’s checkout form, or that row of payment terminals at your café. If any of those touch card data, PCI DSS rules follow. In this post, you’ll learn exactly where those boundaries lie—and why they matter.

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Where Does PCI DSS Apply in Your Organization?

Every device, network, or service that stores, processes, or transmits cardholder data falls under PCI DSS. Let’s break down the main categories.

1. Cardholder Data Environments (CDEs)

• Definition: The CDE includes all hardware and software systems that handle Primary Account Numbers (PANs).
• Examples:
  • E-commerce web servers where your customers enter their card details.
  • Point-of-Sale (POS) terminals in retail stores.
  • Back-end databases that store transaction logs.

2. Connected Third Parties & Service Providers

• Scope: Any vendor that processes or stores your card data must comply.
• Common Providers:
  • Hosted payment page vendors (e.g., Shopify, Stripe Checkout).
  • Cloud gateway services (e.g., Authorize.Net, Braintree).
• Why It Matters: If you outsource payment pages but still control card-data flow, you share responsibility.
• Code Snippet: Sample firewall rules to isolate a payment-gateway server: bashCopyEdit# Allow traffic TO gateway iptables -A FORWARD -s 10.0.0.0/24 -d 203.0.113.50 -j ACCEPT # Block all other access to CDE iptables -A FORWARD -s 0.0.0.0/0 -d 10.0.0.0/24 -j DROP

3. Virtual and Cloud Environments

• In-Scope Components:
  • Virtual Machines (VMs) that handle PAN.
  • Containers or serverless functions processing payments.
  • Managed database services if you hold encryption keys.
• Cloud Provider Responsibilities:
  • The cloud vendor secures the infrastructure (“shared model”).
  • You must secure configurations, encryption, access controls.
• Table: ComponentIn Scope if…NotesVirtual MachinesThey process, store, or transmit PANTreat like physical serversContainersThey handle cardholder dataEach container counts as a hostManaged DatabasesYou manage key rotation & encryptionVerify provider’s PCI attestationServerless FunctionsThey run payment-related codeCode-level controls apply

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Key Factors That Determine PCI DSS Applicability

PCI DSS doesn’t apply uniformly. Four factors influence whether a system or service falls inside the scope.

1. Transaction Volume

• Merchant Levels:
  • Level 1: More than 6 million transactions per year.
  • Level 2: 1 million to 6 million.
  • Level 3: 20,000 to 1 million e-commerce transactions.
  • Level 4: Fewer than 20,000 e-commerce transactions.
• Impact: Higher volumes mean stricter reporting and on-site assessments.

2. Data Flow and Storage Locations

• On-Premise vs. Cloud:
  • On-prem servers are in scope if they hold unmasked PAN.
  • Cloud storage counts if you control encryption keys or access policies.
• Example File-Path Patterns (to scan for PANs): swiftCopyEdit/var/backups/payments/*.csv C:\data\transactions\*.json
• Best Practice: Tokenize or truncate PANs whenever possible to reduce scope.

3. Network Architecture and Segmentation

• Purpose: Reduces the number of in-scope systems by separating CDE from general IT.
• Techniques:
  • VLANs and ACLs to isolate CDE.
  • Firewalls enforcing “deny all” by default.
  • Dedicated switch ports for POS devices.
• Code Snippet: VLAN ACL example for CDE isolation: textCopyEditaccess-list 100 permit ip 172.16.10.0 0.0.0.255 any access-list 100 deny ip any 172.16.10.0 0.0.0.255

4. Third-Party Connections

• What to Watch: Remote access, support tunnels, and API integrations.
• Requirement: Any link that can access the CDE—even maintenance tools—must meet PCI controls.

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Best Practices for Identifying In-Scope Systems

A clear scoping process keeps you efficient and audit-ready. Follow these steps.

1. Conduct a Scoping Assessment

1. Interview Stakeholders: Talk to IT, finance, operations.
2. Map Data Flows: Draw diagrams of how card data moves through systems.
3. Inventory Assets: List all hardware, software, and networks touching PAN.
4. Verify Controls: Check firewalls, encryption, access logs.

2. Leverage Automated Discovery Tools

• Popular Options: Nmap, Qualys, Tenable.io, Rapid7.
• Benefits:
  • Quickly find unknown hosts.
  • Scan for open ports and services.
  • Identify outdated software and misconfigurations.
• Comparison Table: ToolDiscovery DepthReporting DetailCost LevelNmapBasicCLI/TextFreeQualysDeepWeb DashboardHighTenable.ioDeepCustomizableMediumRapid7ModerateIntegrated SIEMMedium

3. Implement Ongoing Monitoring and Re-assessment

• Frequency:
  • Quarterly vulnerability scans.
  • After Changes: Whenever you add new servers or change network topology.
  • Annually: Full PCI DSS audit with a Qualified Security Assessor.
• FAQ
  • Q: How often should you re-scope PCI DSS?
  • A: At minimum quarterly, and immediately after any significant infrastructure change.

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Conclusion

We’ve covered exactly Where Does PCI DSS Apply?:

• All environments handling card data, whether physical, virtual, or cloud-based.
• Key factors like transaction volume, data flow, network segmentation, and third-party links.
• Best practices to map, discover, and monitor your in-scope systems.

Now, take action. Start your scoping assessment today. Engage with a Qualified Security Assessor. Protect your customers—and your reputation.

PCI Security Standards Council – https://www.pcisecuritystandards.org/