PCI Penetration Testing Explained: Requirements, Scope, and Best Practices

• PCI penetration testing is a simulated cyberattack on your payment systems, performed by ethical hackers to find and exploit security weaknesses before criminals do.
• It is required by PCI DSS Payment Card Industry Data Security Standard for any organization that stores, processes, or transmits cardholder data, ensuring you regularly test and harden your defenses.
• The scope includes your entire Cardholder Data Environment CDE and any systems or networks that could impact it from databases and applications to cloud servers and network segments. Proper scoping is critical so no important component is left untested.
• Penetration testing reduces breach risk by validating that security controls firewalls, encryption, access controls, etc. actually withstand real world attacks. It uncovers exploitable vulnerabilities that automated scans might miss, helping you fix issues before attackers can abuse them.
• Organizations should perform PCI pen tests at least annually and after any major changes. In practice, many companies are moving toward more frequent or continuous testing to keep up with evolving threats and maintain continuous compliance.

In today’s digital payment landscape, PCI penetration testing has become a non negotiable practice for merchants, payment processors, fintech platforms, and any business handling credit card data. PCI DSS the industry standard for card security doesn’t just suggest penetration testing it mandates it for those in scope. But beyond ticking a compliance box, penetration testing is about protecting high value targets: modern payment systems are hot targets for cybercriminals because they hold the keys to financial gain. Every credit card number in your databases or payment flows is a potential payday for attackers.

This article demystifies PCI focused penetration testing from a practitioner’s perspective. We’ll clarify what it involves, why attackers are drawn to payment environments, and how it aligns with PCI DSS requirements. We’ll also delve into what a proper PCI penetration test should cover from verifying network segmentation to probing cloud configurations and common pitfalls to avoid. Whether you manage a cardholder data environment on premises or in the cloud, understanding PCI penetration testing will help you secure cardholder data and not just comply, but truly protect your business.

What Is PCI Penetration Testing?

PCI penetration testing is a controlled, ethical hacking exercise against systems in your cardholder data environment. In plain language, it means hiring security professionals to act like attackers and attempt to breach your own payment systems within agreed scope and rules. The goal is to find security gaps before malicious actors do. Unlike a vulnerability scan that only identifies potential issues, a penetration test goes further the tester actually exploits weaknesses to prove they are real and demonstrate the impact. For example, instead of just reporting System X might be vulnerable to SQL injection, a penetration tester will attempt to perform an SQL injection to extract data or gain deeper access, showing what a criminal could achieve.

It’s important to distinguish PCI penetration testing from other security assessments:

• Vulnerability Scanning: An automated scan required separately under PCI DSS Requirement 11.3 that finds known vulnerabilities. Scans are broad but shallow they might flag outdated software or weak configurations. Penetration testing Requirement 11.4, on the other hand, is human driven and goal oriented. The tester uses skill and creativity to chain multiple weaknesses, bypass protections, and actually break into systems. Both are required, but a scan alone is not enough to meet PCI pen test requirements.
• Risk Assessments: These are usually paper based or procedural reviews of risks and controls. A PCI risk assessment like Requirement 12.3 might identify that a database is a high risk asset and should be encrypted, for instance. Penetration testing is the active validation it checks if that database truly is secure can an attacker decrypt it? access it via a flaw? etc.. Think of risk assessments as theoretical and penetration tests as practical verification.

PCI DSS emphasizes exploitation, not just detection, because the act of breaking in provides evidence of which vulnerabilities are truly dangerous. A finding confirmed by exploitation has zero false positives it’s proof that yes, an attacker can do this. The PCI Security Standards Council even published guidance noting that penetration testing helps uncover paths to unauthorized access that automated tools might miss. In short, PCI penetration testing is about actively challenging your security controls under real world conditions to ensure cardholder data is adequately protected.

Why Payment Systems Are Prime Targets

Payment systems sit at the intersection of money and data a combination that attracts cybercriminals like moths to a flame. Cardholder data CHD is extremely valuable on the black market; stolen credit card numbers can be sold in bulk or used for fraud, making any system handling them a lucrative target. This financial incentive drives a variety of attacks against organizations that process payments:

• Web Skimming Magecart style attacks: Online payment pages and shopping carts are frequently targeted by attackers who inject malicious JavaScript to steal card details as customers enter them. These Magecart attacks have compromised major retailers and ticketing sites by exploiting weaknesses in third party scripts or content security on payment pages. If your e-commerce site loads an external script for analytics, chat, etc. without proper controls, an attacker who breaches that third party could alter the script to siphon off card numbers in real time.
• API Abuse: Modern payment platforms often expose APIs for mobile apps or integration with partners. If not properly secured, these APIs can be exploited. For example, a flaw in an authorization API could let an attacker retrieve another customer’s transaction data or personal info. We’ve seen cases of broken object level authorization in payment APIs where simply changing an ID number in a request exposes someone else’s payment records. Attackers are quick to probe payment APIs for such logic gaps or lack of rate limits, which could lead to data leakage or unauthorized transactions.
• Stolen Credentials & Insider Access: Not all attacks are purely technical often the easiest path in is through a valid login. Attackers commonly leverage phishing and infostealer trends to capture employee or contractor credentials, then use those logins to quietly access internal systems. Others deploy automated credential stuffing attack patterns against any exposed login portals like employee VPNs or web admin consoles, trying lists of stolen passwords until one works. Once inside, an attacker can target the CDE from within, essentially turning an external attack into an insider breach. This is why strong authentication and monitoring of internal access to payment systems are so critical.
• Misconfigured Network Segmentation: Many organizations rely on network segmentation to protect cardholder data, isolating the CDE from corporate or guest networks. However, if segmentation is improperly configured e.g. an overly permissive firewall rule or an open port that was forgotten, attackers will find that crack. A common scenario: malware infects a user’s workstation on the corporate network, and because of a firewall misconfiguration, it can reach into a payment server network that was assumed to be isolated. In one fell swoop, what was thought to be out of scope is now a direct path to card data. Poor segmentation turns a small breach into a catastrophic one.
• Third Party Weaknesses: Payment data often flows through multiple parties gateways, processors, SaaS providers, plugins, etc. Attackers will look for the weakest link. If a vendor or partner with network access to your CDE is breached, that can become a stepping stone into your environment. Likewise, if you embed a third party payment widget or rely on a cloud payment service, a security issue on their side could impact you. For instance, if your payment processor’s API is compromised, attackers might intercept or redirect transactions. The target is not just your infrastructure, but the entire supply chain around your payment process.

In summary, payment systems are prime targets because they deal in data that directly equates to money. The impact of a successful attack is high stolen card data leads to fraud losses, hefty fines, legal liabilities, and reputation damage with customers and banks. That’s why PCI DSS places heavy emphasis on securing these systems and why penetration testing is vital: it helps you find and fix the weaknesses that attackers would eagerly exploit for financial gain.

How PCI DSS Defines Penetration Testing

PCI DSS currently version 4.0 explicitly calls out penetration testing as a requirement it’s not optional if you handle card data. Requirement 11 of PCI DSS is titled Test security of systems and networks regularly, and penetration testing is addressed in sub requirement 11.4. In essence, PCI DSS defines penetration testing as a comprehensive security test of your environment, performed by skilled testers, that goes beyond automated scans to validate the effectiveness of your security controls.

Here are key expectations from PCI’s perspective:

• Regular Internal and External Testing: Under PCI DSS 11.4, organizations must conduct penetration tests at least annually for both an external perspective simulating an internet attacker and an internal perspective simulating an insider or someone who already breached the perimeter. You also must test after any significant change in your environment for example, adding a new payment application, network segment, or major infrastructure upgrade. The idea is that your security should be validated continuously, not just at a single point in time.
• Full Scope Coverage: PCI expects the penetration test to cover the entire CDE perimeter and all critical systems. In practical terms, this means the tester should examine not only systems that directly process or store card data, but also systems that could impact the security of those systems. For instance, an Active Directory server that provides authentication for CDE systems, or a jump box used by admins to reach the CDE, must be in scope. If it can affect the CDE, it’s in scope. This also includes testing both network layer security ports, protocols, firewalls and application layer security web applications, databases, APIs for those in scope systems.
• Validation of Segmentation Controls: If you reduce PCI scope by segmenting your network separating the CDE from other networks, PCI DSS requires segmentation testing as part of the penetration test. Requirement 11.4.5 specifically says to test all methods used to isolate the CDE, to ensure no gaps. We’ll discuss segmentation testing in depth later, but essentially the tester will attempt to break out of the CDE or into it from adjacent networks to verify the isolation holds. If any path is found even something small, like an open port or a misrouted connection, that’s a failure of segmentation and must be fixed plus it means those other networks may fall into PCI scope until it’s resolved.
• Documented Methodology: PCI DSS v4.0 places new emphasis on having a defined penetration testing methodology Req. 11.4.1. Organizations need to have a written methodology that the testing follows. This should align to industry standards e.g., NIST SP 800 115, PTES, or OWASP. The methodology should outline how you scope the test, the testing techniques, data analysis, and reporting. During an audit, a QSA might ask to review this methodology document to ensure your pen test wasn’t ad hoc. In practice, using a reputable Penetration Testing Services or experienced internal team often satisfies this, as they bring a standardized approach.
• Tester Qualifications and Independence: PCI doesn’t mandate specific certifications, but it requires that whoever conducts the test is qualified and, if internal, organizationally independent from the systems being tested. Qualified generally means having experience and knowledge in penetration testing techniques and platforms. Many organizations look for certifications like OSCP, GPEN, or CEH as indicators of skill, but more importantly, the tester should have hands-on expertise in testing similar environments. Independence means, for example, your network admin can’t be the one pen testing the network he maintains that conflict of interest undermines the test. If using an internal team, they should report to a separate management chain e.g., under the CISO or an internal audit function. Many businesses opt for an external third party tester to ensure neutrality and breadth of experience.
• Fixing and Retesting Vulnerabilities: A penetration test isn’t a one and done checkbox. PCI Requirement 11.4.4 requires that you address remediate any vulnerabilities found and then re-test to verify the fixes. Simply running a test and getting a report isn’t sufficient you must act on it. If critical vulnerabilities were discovered, you need to patch or mitigate them, and ideally the tester or another qualified party should attempt to exploit the same issue again afterward to confirm it’s truly resolved. QSAs will look for evidence of this remediation and retesting cycle. In audits, it’s common to provide both the initial pen test report and a follow up letter or report showing that specific high risk findings were fixed and re-checked. This proves that the organization didn’t just find problems it fixed them.
• No Check box Testing: The intent behind PCI’s penetration testing requirements is security improvement, not compliance theater. QSAs and the PCI Council have increasingly high expectations for test quality. An annual superficial test that glosses over systems or is done last minute just to generate a report can lead to compliance issues. For example, if a QSA sees a pen test report with very few findings, no clear narrative, or missing scope elements, they might question its validity. Organizations have failed audits because the penetration test was too narrow or executed by unqualified personnel. The takeaway: treating the pen test as a meaningful security exercise ultimately helps with compliance, whereas doing it just for PCI often backfires under scrutiny.

In summary, PCI DSS defines penetration testing as a rigorous, expert driven evaluation of your security, with specific requirements around scope, frequency, and process. It’s about actively testing that your defenses including segmentation work and that you can find and fix vulnerabilities before the bad guys do. Understanding these expectations will help ensure your PCI penetration test meets both the letter and the spirit of the standard.

What a PCI Focused Penetration Test Should Validate

A PCI focused penetration test isn’t just a general pentest; it has certain must validate objectives rooted in protecting cardholder data. When you engage a PCI penetration test, here are the critical things it should confirm:

• CDE Isolation Segmentation Efficacy: If your environment relies on network segmentation to keep the cardholder data environment isolated, the penetration test should rigorously validate that isolation. Testers will attempt to traverse from non CDE networks into the CDE, mimicking an attacker who got a foothold on an adjacent system. Even basic connectivity like a ping or seeing an open port from a non CDE system to a CDE system is a red flag. The expected outcome is that no unintended access routes exist between the CDE and other networks. For example, the tester might place a laptop on the corporate LAN out of scope and try to reach servers in the CDE VLAN all traffic should be blocked. Any holes discovered mean segmentation is not truly effective, which would not only be a compliance issue but a serious security risk. Essentially, the pen test proves that the CDE is a fortress walled off from the rest of your IT environment.
• Ability to Access Cardholder Data: The ultimate risk in any card environment is an attacker retrieving cardholder data e.g., dumping the credit card database or sniffing it in transit. A penetration test should assess whether an attacker could realistically reach and exfiltrate that data. This often means after initial exploitation, the tester will attempt to pivot deeper, say they compromise a web server in the DMZ, can they move from there to the database that stores card numbers? Can they escalate privileges to query sensitive data or decrypt it? For PCI, testers usually won’t extract live card numbers from a database to avoid creating a breach themselves, but they might demonstrate access by retrieving hashed card data, table schemas, or using test accounts. The key is proving that an attack path to CHD exists or confirming that it does not. If your database with PAN Primary Account Number is exposed through a chain of exploits, that’s a critical finding. The test validates whether card data is truly secure in storage and in transit, or if an attacker who breaches one component could snowball that into a full data compromise.
• Lateral Movement and Pivot Resistance: Beyond the direct card data stores, a PCI pen test should evaluate if an attacker can move laterally within the environment to expand their access. Many breaches start on a peripheral system and then pivot towards more critical systems. Testers will try scenarios like: starting on a compromised user workstation or a web server, can they hop to an application server, then perhaps to a database or an admin jump box? They’ll look for weaknesses that allow this progression, such as shared credentials, trust relationships, or missing internal patching. A well segmented, well secured environment will contain an attacker’s movement e.g., the hacked web server has no path to the internal network, or a breached user account doesn’t have permissions to access the CDE systems. The pen test validates those containment measures. If, conversely, the tester finds that compromising one machine opens up several others a domino effect of weak internal security, that’s a major issue to be addressed.
• Security Control Effectiveness: The test should verify that key security controls you rely on are actually effective under real attack. For instance, if you have an intrusion prevention system IPS or web application firewall WAF in front of your payment application, the tester will try to bypass it. They might attempt SQL injection or cross site scripting on your web app and see if the WAF detects or blocks it. If multi factor authentication MFA is required for remote admin access, the tester may check if any system or account bypasses MFA, or if default credentials exist somewhere which happened in some breaches. Essentially, any control that is assumed to protect cardholder data is fair game to test. Does your encryption stop an attacker from reading sensitive files? Does your tokenization of card numbers hold up if the app server is compromised? A PCI pen test report often explicitly states whether critical controls firewalls, ACLs, WAF, access controls, etc. were tested and whether they succeeded or failed in preventing the simulated attacks.
• Adherence to Scope Assumptions: During PCI scoping, you draw boundaries around what’s in scope CDE and connected systems and what’s out of scope. A good penetration test challenges those assumptions. For example, if an adjacent database was left out of scope because it doesn’t store card data, the tester might still attempt to use that database server as a pivot if it’s on the same network. Or if a certain subnet was declared out of scope due to supposed firewall rules, the tester will validate those rules maybe a forgotten rule allows some access. We often find scope creep through testing discovering that a system thought to be isolated actually isn’t. This is valuable, because any system that can talk to the CDE is by definition in scope for PCI. So the test essentially double checks your scoping accuracy. If your scope was too narrow, the pen test will reveal it, giving you a chance to adjust and secure those systems before an auditor or attacker does.
• Resilience of Applications and APIs: Since many payment environments include web applications for customer payments or internal portals and APIs, the penetration test should validate those at a deep level. This means testing for common web vulnerabilities OWASP Top 10 issues like injection flaws, XSS, CSRF, etc. in any app that touches card data. Are forms properly sanitizing input? Can an attacker trick the system into processing an unauthorized transaction or viewing someone else’s payment info? APIs should be tested for auth weaknesses and logic flaws, ensuring, for instance, that one client’s API keys can’t retrieve another client’s data. The tester might also evaluate if your web application firewall is correctly configured e.g., does it block obvious malicious payloads or can they be evaded? By validating the application layer, the test ensures that the places where card data enters or leaves your system are secure.

In summary, a PCI focused penetration test validates the critical security outcomes: that your CDE is properly isolated, that no easy paths lead to card data, that attackers can’t freely roam your network, and that your apps, APIs, and controls are solid. If the test finds those assumptions hold, you gain confidence and evidence that you’re protecting cardholder data effectively. If not, you gain a clear roadmap of what to fix to fortify your defenses.

Typical Scope of PCI Penetration Testing

A key step in any PCI penetration test is defining the scope what systems and components will be tested. PCI DSS scope is determined by the cardholder data environment and anything connected to it. In practice, a PCI pen test scope usually includes the following areas:

Cardholder Data Environment CDE

This is the heart of the scope. The CDE encompasses all systems that store, process, or transmit cardholder data or sensitive authentication data. In a typical business, this might include databases holding payment transactions, application servers processing payments, point of sale POS terminals, card reader devices, and encryption key management systems. Testers will directly assess these systems because they are the crown jewels a compromise here means immediate exposure of card data.

For example, if you have a payment database, the penetration test will try to see if an attacker can reach it either through a direct vulnerability like a misconfigured database service accessible on the network or via another component like a web app that interfaces with the DB. In a retail scenario, if POS terminals are in scope, testers might assess how easily those could be attacked though often POS testing is more specialized. The goal in the CDE segment of testing is to ensure that these systems have robust hardening: up to date patches, strong credentials, secure configurations, and that they aren’t directly accessible except through tightly controlled channels. Any weakness in the CDE systems is high severity, so this portion of the test is often thorough including authenticated testing if possible e.g., using a test account to see more of the system to find hidden flaws. Remember, everything in the CDE is by definition in scope for PCI, so nothing here gets a free pass. If it touches card data, it gets tested.

Payment Applications & APIs

Most cardholder data environments include one or more payment applications for instance, an e-commerce website checkout, a mobile payment app, or back end services that handle card authorizations. These applications and their APIs are a critical part of the scope because they are common entry points for attackers. Here, the penetration test will perform deep application layer testing. This involves looking for issues like SQL injection, cross site scripting XSS, authentication bypass, insecure direct object references IDOR, and other vulnerabilities as catalogued by OWASP. The testers simulate what a malicious user or fraudster might do on the front end: Can they manipulate the payment form? Can they submit unexpected data to the API? Can they retrieve data they shouldn’t like someone else’s card details or personal info?

Special attention is given to how these apps handle cardholder data. For instance, does the web application properly mask card numbers and never store the full PAN unencrypted? Are there any hidden fields or API endpoints that spill sensitive data? Testers also assess the effectiveness of application security controls for example, if you have input validation or a web firewall, can those be evaded with tricky payloads? Given the rise of single page apps and mobile apps, API security is equally important: the test will check that each API endpoint enforces authentication and authorization correctly no leaking data across accounts, no ability to perform unauthorized actions via the API. Engaging specialized web application security testing for login and session flows can be invaluable here, as it ensures things like session management, password resets, and other auth flows are scrutinized. The bottom line: any software component through which card data flows or is accessed gets a thorough workout in a PCI pen test.

Network Segmentation Controls

If you use network segmentation to limit PCI scope, testing these controls is mandatory. Segmentation controls include firewalls, routers with access control lists, VLAN separation, software defined network policies, etc., that create a boundary between the CDE and everything else. In the scope, this often appears as segmentation validation testing. What it entails is the penetration tester actively trying to bypass or slip through those network barriers. They might take a system outside the CDE say, an IT workstation or a server in the corporate network and attempt to ping CDE systems, scan for open ports, or connect to services that should be blocked. They’ll use tools like Nmap to systematically probe the CDE from various points outside it, looking for any crack. Even things like being able to reach a CDE system’s login page from a workstation network when it should be restricted would be a finding.

The expected result is that all such attempts are blocked essentially testing should show a brick wall around the CDE. If any packet gets through that shouldn’t, the tester will investigate why: maybe a firewall rule was misordered or a network route was forgotten. We often find legacy rules that accidentally allow some access or shadow networks like backup networks or management interfaces that bridge CDE and non CDE. Those are critical to identify because if an attacker finds them, your segmentation is effectively compromised. PCI requires that segmentation testing cover all methods in use so if you have multiple firewalls or both on prem and cloud network controls, each mechanism should be validated. Many service providers have to do this every six months. In summary, the scope covers not just systems, but the gaps between systems ensuring the walls that protect cardholder data have no doors left unlocked.

Cloud & Virtualized Payment Systems

With many organizations moving CDE components into the cloud or virtualized environments, a PCI penetration test scope often extends to cloud infrastructure like AWS, Azure, GCP and virtualization platforms. The cloud introduces a shared responsibility: the cloud provider manages the underlying hardware and core services, while you, the customer, are responsible for how you configure and use those services. A PCI pen test in the cloud context will focus on the customer controlled aspects, such as:

• Cloud Configurations: Testers will review and attempt to exploit misconfigurations in cloud resources. This could be an S3 bucket in AWS that’s inadvertently public or not properly encrypted, an overly permissive AWS Security Group or Azure Network Security Group that exposes a sensitive port, or leaked cloud credentials that allow broader access. For example, if your payment application is running on an EC2 or Azure VM, are its management ports SSH/RDP locked down or open to the world? If a storage container holds exported transaction logs, can the tester find a way to read it perhaps it’s publicly accessible or uses a default name?
• Identity and Access Management IAM: Cloud environments rely heavily on IAM roles and policies. A tester will check if any roles have more privileges than they should. Perhaps the web server’s role can access the key management service or database when it shouldn’t. The test might involve trying to escalate privileges within the cloud e.g., using a misconfigured instance role to retrieve sensitive data from a metadata service. Since identity is the new perimeter in cloud, these checks are vital.
• Virtualization Flaws: If you host your CDE on virtual machines whether in cloud or on prem hypervisors, the tester might consider whether any known virtualization escapes or misconfigs could allow hopping between VMs. For instance, if one VM in the CDE is compromised, is there a path to the hypervisor or peer VMs? Direct hypervisor attacks are rare and testing them might violate cloud provider terms, but misconfigurations like a management interface shared by multiple zones can be examined.
• Containerized Environments: If your payment applications run in containers or Kubernetes, the scope will include the container environment. The tester will check for things like container breakout vulnerabilities, overly broad inter container network access by default, all pods may talk to each other a risk if not restricted, and the security of secrets are API keys or encryption keys stored in config files or etcd without proper protection?. They will attempt to exploit any weak points to move between containers or access the underlying node.
• Multi Tenant Separation: If you are a service provider or SaaS handling card data for multiple clients in a shared environment, the pen test should validate that one client’s data cannot be accessed by another. This might involve attempting to cross tenant boundaries via the application or cloud config. PCI v4.0 explicitly calls for testing logical separation controls for service providers e.g., ensuring that each customer’s data and processes are isolated. For example, in an AWS environment, that could mean verifying that one customer’s data in a multi tenant database can’t be pulled by another customer’s account.

Engaging in thorough cloud security testing focused on identity and access paths is essential to cover these scenarios. The scope in cloud/virtualized contexts might not be a physical network range but rather all the cloud resources accounts, subscriptions, VPCs/VNETs, instances, containers, etc. that make up your CDE. The pen tester will often need read only access to cloud consoles or APIs to assess configurations in addition to active testing. The outcome should be a confirmation that your cloud setup is as secure as a traditional on prem setup no inadvertent exposure, no weak credentials, and proper containment of the CDE within the cloud environment.

Third Party Integrations

Modern payment ecosystems are rarely self contained. You may rely on third party services for payment processing, use vendors for support, or integrate outsourced components. While you can’t exactly penetrate test a third party’s systems without permission, the integration points absolutely fall in scope for your penetration test. Key areas include:

• Payment Gateways and External Processors: If your system redirects to or communicates with a payment gateway e.g., Stripe, PayPal, a bank’s API, the tester will evaluate the security of that interaction. For instance, is the redirect URL susceptible to manipulation could an attacker send customers to a look alike malicious page to capture cards? Is the API communication properly authenticated and encrypted? If you store tokens from the gateway, can those tokens be used maliciously to charge cards or reveal data? A breach might not happen in the gateway itself since that’s on them, but if an attacker can alter how your system talks to the gateway, they could divert transactions or skim data.
• Third Party Code and Libraries: Many payment pages include third party JavaScript for analytics, chat, fraud detection, etc.. As noted, this is a common Magecart attack vector. Testers will review what third party content is loaded and may simulate what happens if that content were malicious. PCI DSS v4.0 introduced requirements to inventory and control scripts on payment pages 6.4.3 and 11.6.1. A pen tester might inject a test script or use a proxy to modify a script in transit in a controlled manner to see if your controls catch it. The goal is to ensure that you have measures like Content Security Policy, Subresource Integrity, or monitoring to detect if any third party component is compromised and attempting to steal data.
• Remote Access Paths: Often third party vendors like IT support companies, developers, or QSAs themselves have remote access into systems. All such access points are in scope. The tester will examine things like VPN connections, remote desktop gateways, or vendor maintenance accounts. Are they secured with MFA? Are there default or weak passwords? One classic issue is vendors who manage POS systems using remote desktop tools attackers know to search for those and attempt to crack them. Part of the pen test may involve ensuring all those external access points are locked down and segmented appropriately.
• Upstream/Downstream Service Providers: If you are a service provider for example, a SaaS that handles some part of payments for clients, your PCI pen test scope might include demonstrating to your QSA that your client environments are isolated and that you have no backdoors between them. Conversely, if you’re a merchant using a service provider, you’ll want to ensure that nothing from that provider’s network can bleed into yours except what’s intended. Sometimes, the scope can include a coordinated test where the service provider participates or at least allows certain tests to verify these boundaries.

In summary, anything that touches your CDE from the outside whether it’s a user’s browser, a vendor’s connection, or a partner’s system gets consideration in the scope. The penetration tester’s job is to think like an attacker: if they can’t break your systems directly, can they break something your system trusts? Testing these integration points often reveals indirect weaknesses for example, acceptance of invalid certificates, lack of verification on callback URLs, etc.. By including third party integration security in scope, you ensure there isn’t an unlocked side door into your cardholder data.

Common PCI Penetration Testing Mistakes

Even with the best intentions, organizations often fall into some pitfalls when approaching PCI penetration testing. Here are common mistakes and why they can be dangerous:

• Confusing Scans for Pen Tests: One of the biggest mistakes is thinking that running a vulnerability scanner report fulfills the PCI pen test requirement. It does not. Automated scans even credentialed ones lack the manual verification and exploitation that PCI demands. Simply having a Nessus or Qualys report won’t satisfy a QSA for 11.4 and more importantly, it won’t truly test your security. Over reliance on scanning can lead to a false sense of security scanners can miss logic flaws or chained attacks and will likely result in an audit failure if presented in lieu of a real pen test. Always complement scanning with a human driven penetration test.
• Improper or Incomplete Scoping: Scope mistakes are rampant. Some companies define the scope too narrowly whether intentionally to save cost or by oversight. For example, they might exclude a web application because it doesn’t store card data, not realizing it still transmits card data and is thus in scope. Or they forget that an admin network segment connects into the CDE. If it’s not in the test, it won’t be in the report and a QSA could flag that discrepancy. Worse, an attacker will find the untested path. An incorrectly scoped test is essentially an invalid test. To avoid this, always revisit your PCI scope and include all relevant systems CDE, connected to, security impacting systems, etc.. If in doubt, it’s safer to test a bit more than too little.
• Excluding Cloud Components: With hybrid and cloud environments, another mistake is treating the cloud bits as out of scope or assuming the cloud provider handles it. Remember, your configurations in the cloud instances, storage, IAM, etc. are very much in scope if they handle card data. We’ve seen cases where a company moved some card processing to a cloud microservice but didn’t include that in the annual pen test because the testing vendor only looked at on prem systems. That leaves a huge blind spot. Every storage bucket, serverless function, container, or VM that touches CHD needs testing. Also, ensure your testers have the skills and rights to assess cloud security, not just traditional networks.
• Neglecting Segmentation Testing or Assuming It’s Fine: Some organizations with tight schedules or limited budgets skip a thorough segmentation test, thinking their firewall rules are obviously correct. This is risky. Misconfigurations or rule creep happen more often than you’d think, especially in complex networks. Assuming segmentation is solid without evidence is a compliance and security gamble. PCI explicitly requires segmentation validation failing to do it or doing a very superficial job of it might lead to auditors declaring your whole network in scope if they’re not convinced. The mistake here is not treating segmentation testing with the same rigor as the rest of the pen test. A proper segmentation test might require setting up test VMs in different segments and spending time scanning and trying connections. It’s worth the effort to do it right.
• Conducting Testing Too Late or Infrequently: Often, companies schedule the penetration test right before the PCI audit deadline, thinking it’s just a formality. The test then finds serious issues as it often will, and there’s a scramble with little time to fix them. If those issues can’t be resolved by audit time, you could be in compliance hot water. This mistake is treating pen testing as a yearly fire drill rather than a continuous improvement tool. Ideally, you want to test early enough in your compliance cycle to address findings calmly. Even better, do it more than once a year e.g., test certain high risk areas quarterly, or implement ongoing testing in your CI/CD. This way, you’re not blindsided by major findings at the last minute. Remember that PCI requires retesting after fixes; leave time for that too.
• Lack of Qualified, Independent Testers: Another common pitfall is using someone who isn’t truly qualified or independent to do the test, which can invalidate your effort. For example, assigning an internal sysadmin to run an off the shelf exploit tool on their own network is not a credible test and the sysadmin might be biased to not find problems. Similarly, having a developer test their own code is problematic they might lack the attacker mindset or be blind to their own mistakes. Ensure your testers have solid credentials or experience in penetration testing. If they’re internal, document how you maintain their independence e.g., they report to a different department and had no role in building the systems. QSAs have been known to ask who performed the test and question their qualifications. Don’t cut corners here use a reputable third party or a well trained internal team that’s separate from operations.
• Poor Documentation and Reporting: Sometimes the testing is done well, but the documentation is lacking which is a mistake because PCI is all about evidence. An incomplete report no clear scope listed, no details on methods, or missing proof for findings can undermine the whole exercise. Additionally, not retaining the report and evidence for at least a year is a mistake; you need to have last year’s results on hand for the next audit. Treat the penetration test report like a formal deliverable: ensure it clearly documents what was tested, how it was tested, what was found, and includes necessary details like screenshots or logs for proof. Also track your remediation steps in writing. This way, if auditors or stakeholders have questions, you have everything buttoned up.

Avoiding these common mistakes comes down to approaching PCI penetration testing as a serious security endeavor. Scope it right, do it regularly, use skilled testers, and follow through on fixing issues. That not only keeps the PCI auditors happy but, more importantly, actually improves your security against real threats.

How Often Should PCI Penetration Testing Be Performed?

PCI DSS requires penetration testing at least annually every 12 months and after any significant change. This is the bare minimum for compliance, but there are nuances and best practices to consider:

• Annual Testing The Baseline: An annual external and internal pen test is required for all Level 1 merchants and service providers and generally recommended for others in scope. This means, for example, if you did a test in March this year, you need to do it by March next year again or sooner. The report should be fresh for each yearly PCI assessment. Some smaller merchants who use certain PCI Self Assessment Questionnaires SAQs might have reduced testing requirements, but if you store or process any real card data, annual tests are the norm.
• After Significant Changes: PCI DSS explicitly says you must test after significant changes to your environment. What qualifies as significant change? Typically things like: adding a new network segment or major system to the CDE, a big upgrade of infrastructure or operating systems, deploying a new web application or major feature that touches card data, changes to firewall rules or segmentation, moving a component to the cloud, etc. Essentially, if the change could affect the security of the CDE, you need to re-test those affected parts rather than waiting till the next annual cycle. For example, if you launch a new mobile payment app mid year, you should conduct a focused penetration test on it rather than waiting. This ensures that changes haven’t introduced new vulnerabilities.
• Segmentation Testing Frequency: For organizations using network segmentation to reduce scope, PCI DSS v4.0 requires segmentation controls be verified at least annually for merchants and every six months for service providers. So if you’re a service provider like a data center, cloud service, or payment processor handling multiple clients, you actually need to validate your segmentation twice a year. This recognizes that service provider environments tend to be more complex and high risk. Merchants should do it yearly at minimum, but honestly if you’re making frequent network changes, you might voluntarily do it more often too.
• Continuous and Risk Based Testing: While PCI sets minimums, many organizations are moving toward a more continuous testing approach. Threats evolve quickly new vulnerabilities like the latest critical CVE in an SSL library or database can emerge any time. If you only test once a year, you might have a window of many months where attackers could exploit something you’re unaware of. Some companies adopt quarterly mini pentests or ongoing penetration testing as a service to catch issues sooner. For example, you might do a full blown test annually, but also do targeted tests after each major code release or every quarter focusing on different components. This isn’t required by PCI, but it’s a good security practice. In fact, PCI’s new Customized Approach allows companies to demonstrate strong control effectiveness in flexible ways showing a robust continuous testing program could be a way to exceed the basic requirements.
• Before Audits vs. Throughout the Year: Traditionally, a lot of folks would do the pen test right before the audit to have the latest report. However, as discussed in mistakes, this can backfire if issues are found late. A better strategy is to schedule the annual PCI pen test well before your audit is due say 3-6 months prior so you have time to remediate and retest. Then do a lighter re-check closer to audit if needed. Also, align testing with any big calendar events: if you know you revamp systems in January, plan a test in Feb/March, not in December. Essentially, integrate it into your change management cycle.
• Regulatory and Business Drivers: Keep in mind, beyond PCI DSS, there may be other drivers for testing frequency. For instance, your bank or payment processor might expect to see a recent pen test report more frequently, or you might be subject to other standards like SOC 2, ISO 27001 that also value regular testing. If you had a security incident, it’s wise to conduct a new penetration test afterward to ensure that vulnerability is truly gone and to uncover any other issues the attackers might have missed yes, that happens a pen tester might find additional problems during incident post mortem.

In summary, at least once a year is the rule, but more often is better from a security standpoint. The cadence should match your organization’s rate of change and risk appetite. Fast moving fintech startups, for example, often test much more frequently than annually because their environment can drastically change in a few months. On the other hand, a very static legacy environment might get by with annual tests though even then, new vulnerabilities in old systems can appear. Always test after major changes, and consider supplementary testing if any critical new threats emerge for example, if a major vulnerability like Heartbleed or Log4Shell comes out, you might do an out of band test of exposure to that issue. The goal is to have as few surprise weaknesses as possible by the time your audit or, worse, a real attacker comes around.

FAQs

• Is penetration testing mandatory for PCI DSS compliance?

Yes. If your organization is required to comply with PCI DSS generally, if you process, store, or transmit cardholder data, penetration testing is a mandatory requirement. PCI DSS Requirement 11.4 specifically mandates annual internal and external penetration tests, as well as testing after significant changes. There are a few edge cases for example, very simple payment setups that use only point of sale terminals with no stored data might use a lighter self assessment but any Level 1 merchant or service provider the vast majority of businesses handling cards online or at scale must include pen testing in their compliance program. In short, if you’re handling card data in any IT system, assume you need a penetration test to meet PCI DSS. Failing to do so not only risks non compliance with potential fines or loss of the ability to process cards but also leaves your organization blind to real security weaknesses.

• What’s the difference between PCI vulnerability scanning and penetration testing?

Vulnerability scanning and penetration testing are two distinct but complementary security activities required by PCI DSS. A vulnerability scan PCI DSS 11.3 is an automated scan typically using tools that identifies known security issues missing patches, known misconfigurations, etc. across your systems. Scans are required quarterly external scans must be done by an Approved Scanning Vendor, or ASV and are more frequent, but they only report potential problems. Penetration testing PCI DSS 11.4 is a manual, deep dive test by a skilled professional, required at least annually. The penetration tester will actually attempt to exploit vulnerabilities and simulate how an attacker could break in. The main differences can be summed up as: scanning = automated and broad, pen testing = human and targeted. Another key difference is the output: a scan gives you a list of possible vulnerabilities often with false positives, whereas a pen test gives you confirmed exploits and the impact of those issues with minimal false positives since everything is validated. Both are necessary you use scans to continually catch common issues, and use penetration tests to find the deeper, more complex attack paths and to validate what a real attacker could do with the vulnerabilities found.

• What systems are considered in scope for a PCI penetration test?

In scope will be all components of your Cardholder Data Environment CDE and any other system that can connect to or affect the security of the CDE. Concretely, this includes: systems that store card data databases, servers, process it applications, payment terminals, or transmit it network devices, APIs. It also includes systems that don’t handle card data themselves but are on the same network or have access into the CDE often called connected to systems. Examples: a web server in a DMZ that communicates with a database in the CDE, or an internal jump server used by admins to reach CDE servers. Additionally, any security systems that could impact CDE security like authentication servers, DNS servers used by CDE systems, etc. should be in scope. Basically, if compromising System X could in any way lead an attacker to cardholder data in System Y, then X is in scope to test. Note that if strong network segmentation is in place, systems on the other side of a properly isolated network can be considered out of scope but the segmentation itself then must be tested to confirm those systems truly have no access. One way to think of it: draw a boundary around everything that touches CHD directly or indirectly that’s your testing scope. If in doubt, include it. It’s better to show an auditor you tested a few extra systems than to have missed one that should have been included.

• Does PCI DSS 4.0 change penetration testing expectations compared to the old version?

Yes, PCI DSS 4.0, which becomes fully mandatory by 2025, introduces some updates that raise the bar for penetration testing. The core requirement of annual internal/external tests remains, but v4.0 puts more emphasis on methodology and continuous improvement. For instance, 4.0 explicitly requires you to have a documented, industry standard methodology for pen testing, whereas earlier you just had to do it. It also adds clarity around testing segmentation controls 11.4.5, making it clear you must test every segmentation method and do it more frequently for service providers. Another change is the introduction of the Customized Approach in v4.0: if you choose to meet security objectives with alternative controls, you need to do targeted risk analyses and likely more rigorous testing to prove those custom controls work. Additionally, PCI DSS 4.0 has a new requirement for authenticated vulnerability scanning 11.3.1.2 while that’s a scan, not a pen test, it means internally you’ll have more information about vulnerabilities, which typically results in a more informed penetration test testers can use those authenticated scan results to focus their exploits. Also, requirement 11.4.7 in v4.0 addresses service providers supporting their customers’ penetration testing meaning if you’re a cloud or hosting provider, you need to allow customers to pen test their environment on your platform. In summary, v4.0 doesn’t remove any pen testing it reinforces and clarifies it, expecting organizations to be more structured and perhaps more frequent in their testing, with no stone unturned network, applications, segmentation, all need to be covered.

• Who should perform a PCI penetration test can we do it ourselves?

PCI DSS allows either internal or external personnel to perform the penetration test, but there are strict conditions. The testers must be qualified and independent. Qualified means they have the skills and experience to do a proper job typically this means having a solid background in penetration testing and possibly certifications like OSCP, CEH, GIAC GPEN/GWAPT, etc., or demonstrable experience in similar environments. Independent means the tester is not part of the team that maintains the systems being tested and has no vested interest in the outcome. In practical terms, most organizations choose to hire an external security firm specializing in penetration testing for their PCI tests. External testers have the advantage of broad experience and no internal bias; plus their reports may carry more weight with auditors. If you use internal staff, you need to ensure, for example, that your tester from the security team is free to test the systems without influence and isn’t testing their own work. Many companies with internal red teams still bring in third party testers annually for PCI to get an objective review. Another consideration is that the QSA might ask about the tester’s qualifications having a well known firm or certified individuals can streamline that conversation. So, while you can do it yourself if you have a skilled internal team separate from IT operations, most opt to use specialized penetration testers to meet PCI requirements and to get the most value out of the test.

• Do we need a PCI penetration test if we use a third party payment provider and don’t store card data ourselves?

Even if you fully outsource payment processing or use tokenization such that you don’t store actual card numbers, you may still need a penetration test it depends on your setup. If any part of your environment is involved in processing or transmitting card data, that part is in scope for PCI. For example, say you have an e-commerce site that uses a hosted payment page from a provider: your site might redirect customers to the provider’s domain for payment entry which would be out of your scope, but the pages doing the redirect on your site are still in scope. You’d want to test that those pages or scripts can’t be tampered with imagine an attacker altering your redirect to send customers to a fake page. If you have a mobile app that collects card data and sends it directly to a processor, you need to test that app to ensure it isn’t vulnerable to interception or tampering. In short, outsourcing reduces scope but doesn’t eliminate it. Typically, you end up with at least your web environment in scope SAQ A EP situations, for instance, require pen testing of the web server that touches cardholder data via redirect. If truly nothing in your environment handles card data SAQ A where even the form is hosted elsewhere and you only have maybe a confirmation page, your PCI obligations are lighter but even then, best practice is to test the interfaces to ensure an attacker can’t change the integration. Also remember, even if a provider handles the heavy lifting, a breach on your site that skims card data as it’s entered before it goes to the provider would be your responsibility. So it’s wise to have a penetration test cover any customer facing components or integrations involved in the payment process, even if you don’t store the data. And if you’re a service provider yourself, you definitely need to test your own infrastructure as part of your PCI compliance.

PCI penetration testing is about security validation, not just compliance checkboxing. By simulating real world attacks on your cardholder data environment, you gain an unvarnished view of where your defenses are strong and where they need improvement. In an era where payment systems are prime cyber targets, this kind of proactive testing is crucial. Remember that the true goal isn’t just to pass a PCI audit it’s to prevent breaches. A thorough PCI pen test, followed by diligent remediation, reduces the risk that your organization will become the next data breach headline. In summary, when done right, penetration testing transforms PCI requirements into real world security outcomes, helping you protect cardholder data and maintain the trust of customers and partners alike.

Ready to Strengthen Your Defenses? The threats of 2025 demand more than just awareness; they require readiness. If you're looking to validate your security posture, identify hidden risks, or build a resilient defense strategy, DeepStrike is here to help. Our team of practitioners provides clear, actionable guidance to protect your business. Explore our Penetration Testing Services to see how we can uncover vulnerabilities before attackers do. Drop us a line, we’re always ready to dive in.

About the Author: Mohammed Khalil is a Cybersecurity Architect at DeepStrike, specializing in advanced penetration testing and offensive security operations. With certifications including CISSP, OSCP, and OSWE, he has led numerous red team engagements for Fortune 500 companies, focusing on cloud security, application vulnerabilities, and adversary emulation. His work involves dissecting complex attack chains and developing resilient defense strategies for clients in the finance, healthcare, and technology sectors.