PCI DSS Compliance Skill

PCI DSS Structure — 12 Requirements and 6 Goals

PCI DSS v4.0.1 organises its 12 requirements under 6 overarching goals:

Consult references/pci-dss-requirements.md for all 12 requirements with key sub-controls and evidence requirements.

Core Concepts

Cardholder Data Environment (CDE)

The CDE is the system components, people, and processes that store, process, or transmit cardholder data (CHD) or sensitive authentication data (SAD), plus any system that can impact their security.

Account data types:

• PAN (Primary Account Number) — the card number; the core element that triggers PCI DSS scope
• Cardholder Name, Expiry Date, Service Code — CHD; can be stored if protected
• SAD (Full magnetic stripe/chip data, CVV/CVC, PINs) — must never be stored after authorisation

Scope reduction strategies:

• Tokenisation — replace PAN with a token; removes tokenised systems from CDE scope
• Point-to-Point Encryption (P2PE) — validated P2PE solutions can dramatically reduce scope
• Network segmentation — isolate the CDE from out-of-scope networks (not required but strongly recommended)

Merchant Levels and Validation Requirements

Merchants:

Service Providers:

Defined Approach vs Customised Approach (New in v4.0)

The Customised Approach requires a Targeted Risk Analysis (TRA) for each customised control, approved by senior management, and assessed by a QSA.

SAQ Selection Guide

Consult references/pci-dss-saq-guide.md for the full SAQ selection decision tree and per-SAQ control counts.

Quick reference:

Core Workflows

1. CDE Scoping

When asked to help scope the CDE:

1. Ask: What data flows involve PANs? (intake, processing, storage, transmission channels)
2. Identify all system components that store, process, or transmit CHD/SAD
3. Identify connected systems that could impact CDE security (jump hosts, monitoring, AD)
4. Assess network segmentation: is the CDE isolated from out-of-scope networks?
5. Identify scope reduction opportunities (tokenisation, P2PE, outsourcing)
6. Produce: In-scope system inventory, data flow description, segmentation assessment, scope reduction recommendations

Scoping rules:

• Any system that stores/processes/transmits PAN → in scope
• Any system connected to a CDE system without adequate segmentation → in scope
• Cloud components that touch CHD (even briefly) → in scope
• Third-party service providers that could impact CDE security → must be PCI-compliant

2. Gap Assessment

When asked to assess compliance against PCI DSS v4.0.1:

1. Ask for: merchant/SP level, in-scope systems, existing controls, SAQ type or ROC requirement
2. Produce a table for each of the 12 requirements with sub-controls
3. For each control: Status (Compliant / Partial / Non-Compliant / N/A), Gap Description, Evidence Needed
4. Highlight critical findings (any non-compliant SAD storage, lack of MFA, no ASV scans)
5. Offer remediation roadmap

Status definitions:

• ✅ Compliant — control is fully in place and operating effectively with evidence
• 🟡 Partial — some controls exist but gaps, exceptions, or inconsistencies remain
• ❌ Non-Compliant — control not implemented; compensating control or remediation required
• N/A — not applicable to this environment with documented justification

3. SAQ Selection

When asked which SAQ applies:

1. Ask: Merchant or service provider? How are card transactions accepted? (card-present, CNP, e-commerce, MOTO)
2. Ask: Is all cardholder data processing outsourced to a PCI-compliant third party?
3. Ask: Are P2PE validated devices used exclusively?
4. Ask: Is there any card-present processing?
5. Walk through the decision logic to select the correct SAQ type
6. Explain what controls the selected SAQ covers and what is excluded from scope

4. Control Implementation Guidance

For any PCI DSS requirement or sub-control, structure your response as:

Requirement [X.X]: [Name]

• What it requires: Plain-language description
• How to implement: Concrete, actionable steps
• Evidence for QSA: What a QSA or ISA will look for during assessment
• Common gaps: What organisations typically miss or get wrong
• v4.0 note (if changed from v3.2.1): What is new or different

5. Policy Generation

When generating PCI DSS-aligned policies:

• Include: Purpose, Scope, Policy Statement, Roles & Responsibilities, Standards/Procedures, Review Cycle, PCI DSS Requirement references
• Include document control block: Version | Author | Approved By | Date | Next Review

Common PCI-aligned policies:

v4.0 Key Changes from v3.2.1

Compensating Controls

When a requirement cannot be met due to a technical or business constraint, organisations may implement a Compensating Control (Defined Approach only). Requirements:

1. Must meet the intent and rigour of the original requirement
2. Must go above and beyond other PCI DSS requirements
3. Must be commensurate with the additional risk from not meeting the requirement
4. Must be documented in the ROC/SAQ with a Compensating Control Worksheet (CCW)

Compensating controls are not available under the Customised Approach — the TRA process serves a similar function there.

Reference Files

Load the appropriate reference file based on the task:

• references/pci-dss-requirements.md — All 12 requirements with key sub-controls, evidence requirements, and common gaps
• references/pci-dss-saq-guide.md — Full SAQ selection decision tree, per-SAQ control scope, and applicability criteria
• references/pci-dss-v4-changes.md — Complete v3.2.1 → v4.0/v4.0.1 change log including all new and modified requirements

When to load reference files:

• Gap assessment → load pci-dss-requirements.md
• SAQ selection → load pci-dss-saq-guide.md
• User asks about v4.0 changes or is transitioning from v3.2.1 → load pci-dss-v4-changes.md
• Control implementation for specific requirement → load pci-dss-requirements.md
• QSA/ROC preparation → load all three files

Disclaimer

Outputs from this skill are informational guidance based on PCI DSS v4.0.1 (PCI SSC, June 2024) — a publicly available standard. This skill does not constitute legal, audit, or professional compliance advice. PCI DSS assessments must be conducted by a Qualified Security Assessor (QSA) or Internal Security Assessor (ISA) for formal compliance validation. Always verify against the official PCI DSS v4.0.1 standard from the PCI Security Standards Council at pcisecuritystandards.org.