PCI Penetration Testing: A Step-by-Step Guide
Learn how to protect cardholder data and maintain compliance with our complete guide to PCI penetration testing.
The Payment Card Industry (PCI) doesn't mess around when protecting credit card data—and for good reason. Verizon’s 2024 Data Breach Investigations Report Retail Snapshot revealed that attacks involving the exploitation of vulnerabilities increased 180% compared to the previous year.
One of the most powerful tools for payment card industry data security is the PCI Penetration Test. This test is designed to find vulnerabilities in your systems—such as weak passwords, gaps in Multifactor Authentication (MFA), and excessive user permissions—before real attackers do.
The PCI Security Standards Council provides detailed instructions on conducting these tests. The guide is comprehensive but complex, so we've put together an overview of the testing process for a more accessible read.
What is PCI DSS Penetration Testing?
Payment Card Industry Data Security Standard (PCI DSS) penetration testing is a mandatory security assessment that actively seeks out vulnerabilities in your Cardholder Data Environment (CDE). This is specifically important for any organization that handles credit card information.
The primary goals of a PCI penetration test are to identify if and how attackers could gain unauthorized access to sensitive systems and cardholder data, and verify that required PCI DSS security controls—such as, vulnerability management, network segmentation, and access control—are properly implemented and effective
Testing approaches typically fall into three categories:
White-box testing: Simulates an attack from someone with insider knowledge. Testers receive complete network and application details, including network diagrams, system configurations, source code, and documentation.
Grey-box testing: A middle-ground approach where testers receive partial system information, such as basic network architecture and limited credentials. It balances realistic attack scenarios with testing efficiency, as testers must still discover many system details independently while having enough context to focus their efforts effectively.
Black-box testing: Replicates an external attacker scenario in which testers begin with no internal system knowledge. They work solely with publicly available information and target IP addresses or domains, discovering vulnerabilities through external reconnaissance and testing.
Most PCI DSS penetration tests use white-box or grey-box approaches, as they provide more accurate and comprehensive results while requiring fewer resources than black-box testing.
Penetration Testing vs. Vulnerability Scan
Penetration testing and vulnerability scans each play a distinct role in cybersecurity. A vulnerability scan identifies potential weaknesses in your systems. Pen testing goes a step further, verifying whether attackers can use these detected weaknesses as a breach point.
Here's how they differ:
Penetration Tests | Vulnerability Scans |
Conducted annually and after significant changes Take days or weeks to complete Use both manual and automated techniques Require qualified security professionals Provide detailed exploitation methods and specific risks | Run quarterly using automated tools Complete within minutes to hours Identify and rank potential vulnerabilities Must use Approved Scanning Vendors (ASVs) for external scans Generate reports based on CVSS (Common Vulnerability Scoring System) scores |
PCI Penetration Test vs. Regular Penetration Test
A regular penetration test is a broad security check, useful for overall cyber health. Businesses choose it to find and fix potential vulnerabilities. A PCI penetration test, on the other hand, specifically safeguards cardholder data and is mandatory for businesses handling credit card transactions.
Here's what sets them apart:
| PCI Penetration Tests | Regular Penetration Tests |
Scope and Requirements | Targets the Cardholder Data Environment (CDE), covering both external and internal networks Must occur annually and after major changes | Can cover any system without specific compliance requirements Usually conducted annually or as determined by a risk assessment. |
Methodology | Must examine both network and application layers Specifically verify PCI DSS security controls Results must be documented and retained for compliance purposes | Both types may use social engineering and vulnerability assessment Follow broader security and data assessment approaches Reports follow internal security policies |
Who Performs PCI Penetration Tests?
PCI penetration tests are conducted by qualified security professionals, often called penetration testers or ethical hackers. These experts are trained to identify system vulnerabilities using the same techniques as malicious hackers, but with the goal of improving security.
Penetration testers typically follow established testing frameworks to ensure comprehensive assessments. Common methodologies include:
The Open Source Security Testing Methodology Manual (OSSTMM)
The Penetration Testing Framework
Your testing team can be either internal or external. If you choose the former (someone from your security team), they must be organizationally independent from the systems being tested, possess documented penetration testing experience, and follow industry-accepted testing methodologies.
If you engage external cybersecurity firms that specialize in PCI DSS assessments, make sure you evaluate their experience, client portfolio, industry reputation, and specific expertise with PCI testing.
The Components of a PCI Penetration Test
A PCI DSS penetration test encompasses scope definition, test execution, analysis of findings, remediation planning, and documentation. Let's examine each component in detail.
Scope
Penetration test scoping sets clear boundaries for testing the Cardholder Data Environment (CDE). Security experts work with your organization to map out what needs testing and create a plan that covers all essential components.
The scope includes:
CDE Perimeter and Critical Systems: Testing examines systems that handle cardholder data and their security controls. This means examining payment processing systems, databases, and the infrastructure that supports them to ensure proper card data protection.
External Perimeter: Checks internet-facing systems like web servers,APIs, firewalls, and VPNs, that attackers might target first. This includes testing for security gaps, such as misconfigurations, unpatched vulnerabilities, and potential unauthorized access points.
Internal Perimeter: Looks at what could happen if someone gets inside your network—how they might move around and what they could access. This includes testing network segments and checking if systems are properly isolated.
Critical Network Connections and Access Points: The test reviews every way into the CDE, from employee access to system connections and maintenance tools. Testers look closely at privileged access paths, connections to other companies, and admin tools that someone could use to get unauthorized access.
Application Layer and Network Layer Testing
The penetration test looks at two main technical areas: application layer security and network layer security.
In the former, testers examine web applications, APIs, and custom software that process card data and check how the applications handle user login, manage sessions, validate data, and protect transactions. Apps get special attention because they often provide direct paths to card data.
The latter examines firewalls, routers, and network Segmentation to ensure proper security configurations are in place. Testers verify that network security works correctly and look for any gaps in the defenses. They also ensure that the CDE stays separate from non-PCI systems and that all security controls function as intended.
Segmentation Checks
Network segmentation testing verifies that your CDE is properly isolated from other business systems. Merchants are required to perform these checks annually, and service providers who use segmentation controls like firewalls or VLANs to reduce their PCI DSS scope are required to perform them every six months.
During testing, security professionals verify that segmentation controls work effectively by examining boundary devices, monitoring network traffic patterns to detect unauthorized pathways, and mapping all connections into and out of the CDE to identify any security gaps. The goal is to ensure that no unauthorized access points or hidden pathways exist between segmented environments.
You must perform additional segmentation checks whenever you make significant changes to your network architecture. System changes or new connections could create unexpected paths into your CDE if they aren’t properly tested.
Social Engineering
Social engineering testing, while optional for PCI DSS compliance, helps organizations assess how well their security awareness training works in practice. Common tests include:
In-person interactions
Phishing simulations
Remote authentication attempts
Password reset tests
Organizations can scale testing based on their business size, industry risk level and security maturity. A small business with strong security controls may require less extensive testing than a large enterprise handling millions of transactions. What matters is getting meaningful insights that match your security needs and resources.
If you choose not to conduct social engineering tests, document your reasoning as part of your risk management strategy. And when tests do reveal gaps, use those findings to improve your security awareness training. The goal is to help your team recognize and respond to common social engineering tactics that could compromise cardholder data.
The 3 Steps of a PCI Penetration Test
PCI penetration testing follows a structured approach with three main phases. The process starts with planning and information gathering, moves into active testing and evaluation, and concludes with detailed reporting and verification of fixes.
Here's how each phase works:
1. Pre-Engagement
The pre-engagement phase, which typically takes one to two weeks, sets the groundwork for the test. The expected outcome is a clear, agreed-upon plan that includes success criteria, testing methodology, and the scope of systems to be tested.
At this stage, you should:
Schedule a kick-off call to review the rules of engagement and establish expectations.
Complete the testing questionnaire and authorization forms.
Define success criteria and testing methodology.
Establish the scope of systems to be tested.
Determine and clarify testing conditions and limitations.
2. Engagement
The engagement phase, which can last between two and four weeks, is when active testing and vulnerability exploitation takes place. At this stage, testers work to identify vulnerabilities and simulate real-world attacks. The aim is to actively test the resilience of your systems and identify weaknesses.
The expected outcome is a thorough identification and assessment of vulnerabilities within the scope, which will provide a clear picture of potential risks.
Engagement begins with the following discovery steps to provide the information needed to complete the attack and execution actions:
Compare the defined scope with the latest ASV report
Gather open-source intelligence (OSINT) to identify potential attack vectors
Validate assets with the client and confirm which systems are in scope
Map applications and services to ensure thorough coverage
Identify and assess potential vulnerabilities
Then, the test progresses to the attack and execution activities that test the strength of your security:
Enumerate public services to identify exposure points
Perform vulnerability mapping to assess the security of applications and services
Test for critical vulnerabilities such as those in the OWASP top 10
Attempt exploitation of identified weaknesses
Execute post-exploitation techniques when authorized to determine how attackers could escalate access
This phase actively tests the resilience of your systems and identifies weaknesses in real-world scenarios.
3. Post-Engagement
The post-engagement phase, usually taking an additional one to two weeks, involves analyzing findings, providing remediation advice, and documenting the results for future reference. The expected outcome here is a comprehensive report that details the vulnerabilities found, their root causes, and remediation recommendations.
In the final stage, testers document results and prepare recommendations. This process includes:
Meeting with the client to discuss preliminary results and explain the findings.
Analyzing root causes of vulnerabilities to understand how they were exploited.
Developing remediation recommendations to fix vulnerabilities and improve security posture.
Documenting all findings, even those that do not directly affect cardholder data.
Verifying remediation of high and medium-severity vulnerabilities.
This phase concludes the penetration testing process with actionable insights that help the organization improve its security, ensure compliance, and prepare for future assessments.
The PCI Penetration Test Report
A comprehensive PCI penetration test report documents the test's security findings, offering a detailed account of vulnerabilities and risks. It helps businesses understand their security posture, prioritize remediation, and ensure compliance.
Businesses should consider prioritizing the following findings:
Exploited vulnerabilities requiring immediate remediation
Potential risks that weren’t exploited but should still be addressed
Firewall misconfigurations that may lead to unauthorized access
Unauthorized traffic patterns indicating possible attack vectors
Application vulnerabilities that could compromise the environment
The Severity Score
Penetration testers use severity scores to help organizations prioritize which vulnerabilities need immediate attention. While many use the Common Vulnerability Scoring System (CVSS) as a standardized measure, scores may be adjusted based on your specific environment and risk factors.
For example, a vulnerability rated as "medium" by CVSS might receive a higher severity score if it could directly impact cardholder data in your environment. Conversely, a "high" CVSS vulnerability might be downgraded if compensating controls in your environment reduce its potential impact. These adjustments should be clearly explained in the report to maintain compliance transparency and help guide your remediation efforts.
Evidence Retention
PCI DSS requires you to maintain detailed records of your penetration testing activities and results. This documentation serves multiple purposes: it demonstrates compliance during audits, tracks your security improvements over time, and provides valuable context for future testing.
Your retention records should include the original testing report, any retesting results, and documentation of remediation efforts. Keep detailed evidence of testing methodologies, scope definitions, and discovered vulnerabilities.
These records need to be securely stored and accessible for at least a year, though many organizations maintain them longer to track security trends and demonstrate consistent compliance.
Report Structure Guidelines
The PCI Security Standards Council outlines common elements for penetration testing reports, though the exact format may vary between organizations. A typical report includes:
Executive Summary with high-level findings and recommendations.
Detailed Scope Statement outlining the systems tested.
Penetration Testing Methodology Documentation to explain how the test was conducted.
Clear Limitations and Restrictions to highlight any testing constraints.
Testing Narrative outlining the steps taken during the engagement.
Segmentation Test Results detailing how effective segmentation measures were.
Comprehensive Findings with risk rankings and technical details.
Technical References with specific targets affected by vulnerabilities.
Post-Test Cleanup Instructions outlining how to handle the results and test data securely.
A structured report allows stakeholders to understand the security landscape, make informed decisions, and ensure compliance with PCI DSS standards.
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PCI Penetration Testing Frequently Asked Questions (FAQs)
Below we answer some of the most common questions about PCI DSS penetration testing.
Is Penetration Testing Required for PCI DSS?
Yes, penetration testing is required for compliance under the PCI DSS Requirement 11. 4. Organizations must conduct annual penetration tests (or even quarterly, depending on your business’s needs) to assess the security of systems storing, processing, or transmitting cardholder data.
What are the Requirements of PCI Penetration Testing?
PCI DSS Requirement 11. 4 specifies requirements for:
Who performs the test: A qualified internal team or external vendor who has documented penetration testing expertise and remains independent from the systems being tested.
Scope: The cardholder data environment and any systems or networks connected to it that could impact payment card security.
Testing frequency: Annual testing for both merchants and service providers, plus after significant changes. Service providers must also conduct segmentation testing every six months.
Testing methodology: Must follow documented industry standards and PCI guidelines with clear procedures and rules of engagement.
Core components: Assessment of network segmentation, application security, and network layer defenses.
Documentation: A detailed report of all findings, including severity scores and clear descriptions of discovered vulnerabilities.
Remediation: All high and medium-risk external vulnerabilities must be fixed, along with high-risk internal vulnerabilities and any segmentation failures that expose the CDE.
Who Performs PCI Testing?
PCI penetration testing must be performed by professionals with documented testing expertise who are independent from the systems being tested. This can be either:
Internal security teams: Your own security professionals can conduct testing if they are organizationally separate from the systems being tested and have proven penetration testing experience.
External testing providers: Third-party security firms that specialize in penetration testing and PCI DSS assessments can be engaged.
Note that while Qualified Security Assessors (QSAs) and Approved Scanning Vendors (ASVs) play important roles in PCI compliance, penetration testers do not specifically need these credentials for penetration testing. What matters is that your testers understand industry-standard methodologies and can thoroughly evaluate your cardholder data environment.
What’s the PCI Testing Process?
PCI penetration testing follows three main phases:
Pre-engagement: The team defines the testing scope, gathers system information, and establishes rules of engagement. This phase sets clear boundaries for what will be tested and how testing will occur.
Active testing: Testers examine the Cardholder Data Environment (CDE) using approved tools and methods. This includes network scanning, application testing, and attempting to identify security weaknesses that could expose card data.
Post-engagement: The team documents findings, assigns severity scores, and creates a detailed report with remediation guidance. This phase may also include retesting to verify that fixes work properly.
Throughout each phase, testers maintain detailed documentation to demonstrate compliance with PCI DSS requirements and support ongoing security improvements.
