PCI DSS & penetration testing: Securing online retail transactions 

The Payment Card Industry Data Security Standard, or PCI DSS, is a set of globally recognised requirements designed to ensure that all companies that process, store, and transmit credit card data continually maintain a secure environment. 

It doesn’t matter whether you’re a small independent store or a large e-com brand, if your business handles payment data directly or through a payment gateway, PCI DSS applies to you. 

The stakes are even higher for online retailers as they face regular attacks from cybercriminals looking to exploit checkout flows, inject malicious code or skim payment data. By ensuring compliance with PCI DSS, retailers can help create a secure transaction environment and as a result build trust with customers, partners, and payment providers. 

Pen testing is outlined specifically in Requirement 11.3 as a critical component of PCI DSS and ensures that your systems are assessed using real-world attack techniques so vulnerabilities can be identified and remediated before they are exploited. Even seemingly insignificant weaknesses in applications or infrastructure could be used as part of a chain to compromise payment data or customer information. 

If your organisation uses segmentation to isolate the Cardholder Data Environment (CDE) from the rest of your infrastructure, PCI DSS requires you to test those segmentation controls as part of your penetration testing. According to Requirement 11.3.4, this must be done at least annually, and after any changes to the segmentation controls. The goal is to ensure the segmentation is effective and that no systems outside the CDE can inadvertently access cardholder data. A properly implemented segmentation can reduce your PCI DSS scope, but only if its boundaries are well defined, maintained, and validated through rigorous testing. 

 Put simply, your entire e-commerce environment is in scope, from the customer facing website and checkout flow, to the backend systems, APIs, cloud infrastructure, and any other internal segments that process or store sensitive cardholder data. 

Pen tests should also ideally be conducted by qualified individuals or third-party providers, such as Bulletproof, who are independent of the systems being tested to ensure objectivity and accuracy. 

Meeting PCI DSS standards is only one side of the security equation, understanding what you’re up against is the other, and as cyber threats evolve so quickly, even the most secure looking e-commerce platform can be vulnerable to attacks if security gaps go unnoticed. 

Here are some of the more prevalent attack methods that payment data and customer accounts in retail environments are targeted with today: 

Common threats to e-commerce security 

Magecart attacks 

Magecart attacks involve malicious JavaScript injected into online checkout pages, often via compromised third party scripts or plugins. And the goal of this attack is to stealthily collect cardholder data as it’s entered onto the page by unsuspecting customers. 

Card skimming 

Card skimming isn’t only a physical world threat. Nowadays, digital skimmers can exploit security weaknesses in your website’s code or payment gateway integration, to silently harvest payment information in the background. 

Account takeovers (ATO) 

Attackers can use stolen or re-used credentials from previous breaches to hijack user accounts through a method known as automated credential stuffing, or targeted brute-force techniques. Once inside, the attacker can access stored card details, personal data, and other information like loyalty rewards, often going unnoticed. 

Broken access controls 

These vulnerabilities allow users to access restricted areas, like other customer accounts, admin panels, or profile data, without proper authorisation. Often caused by misconfigured permissions or insecure direct object references (IDOR), broken access controls are one of the most common real-world issues in web applications. 

As you’ll be aware by now, pen testing doesn’t just uncover security flaws but also plays a key role in meeting PCI DSS compliance requirements and proving your commitment to the secure handing of cardholder data. 

Regular pen testing sends a clear signal to auditors, banks, and customers that you as a business are proactively addressing and preventing weaknesses in your e-commerce environment. 

How penetration testing fits into the bigger picture 

• Prevents surprises during audits – a thorough pen test will highlight vulnerabilities in time for you to fix them before a PCI DSS assessment and avoid non-compliance. 

• Builds trust with third parties – regular pen testing demonstrates proactiveness and reassures banks, payment providers, and your customers that you take security very seriously. 

• Supports other security investments – pen testing works perfectly hand in hand with broader tech stacks such as Web Application Firewalls (WAFs) and Managed SIEM, validating their effectiveness and flagging any security gaps or misconfigurations.