Evan Schuman's StorefrontBacktalk

A 403 Labs QSA, PCI Columnist Walt Conway has worked in payments and technology for more than 30 years, 10 of them with Visa.

PCI DSS has two sunsets coming up. The first is the well-documented end of PA-DSS v1.2 this October. The second, and equally significant, sunset is Windows XP’s end-of-life just a few months later, and this event may have an even more direct impact on retailers.

The demise of Windows XP will challenge retailers with POS or other payment applications running in that environment. These retailers will fall into one of three scenarios, described below. How they choose to address the situation will affect their PCI compliance and, more importantly, their security. There may even be a little fallout for the PCI Security Standards Council (PCI SSC) itself.

On April 8, 2014, about 14 short months from now, Windows XP will reach the end of its life as an operating system. That means that starting on April 9, 2014, Microsoft (NASDAQ:MSFT) will no longer market, support or provide regular security patches for that operating system. Retailers with POS or other payment systems running on Windows XP after this date will, therefore, no longer be PCI compliant.

Retailers running POS applications on Windows XP must act without delay. According to Microsoft: “If your organization has not started the migration to a modern desktop, you are late.”

Why does an end-of-life operating system cause a retailer to be noncompliant? After all, the term “end-of-life” appears nowhere in the PCI DSS. A search of the FAQ on the PCI SSC’s Web site also turns up nothing.

Merchants cannot continue to use a payment application based on an end-of-life operating system, because that end-of-life condition runs up against PCI DSS Requirement 6.1. This requirement states merchants must: “Ensure that all system components and software are protected from known vulnerabilities by having the latest vendor-supplied security patches installed. Install critical security patches within one month of release.” Once an operating system (or an application) goes past its end-of-life, the vendor does not keep an eye out for new vulnerabilities or release any new security patches.

In addition, and aside from PCI DSS compliance issues, retailers with end-of-life operating systems put themselves squarely in every hacker’s cardholder data breach bulls-eye. The bad guys scan merchants’ networks for weaknesses, and an end-of-life operating system may be an open invitation for them to do their worst—particularly when unpatched vulnerabilities are spotted.

Retailers with Windows XP POS or payment applications likely will fall into one of the following scenarios.

Scenario 1: “We are OK; we can migrate to my vendor’s PA-DSS validated versions for, say, Windows 7 or Windows 8.” To confirm this situation, retailers must check the PCI SSC’s list of PA-DSS validated applications. Look under the “Tested Platforms/Operating Systems” part of the table to see what options are available.

A quick check of the PA-DSS list showed many applications that run on Windows XP also have alternate validated versions available. Some questions for retailers in this scenario are: How difficult will it be to change operating systems? What other systems in the payment environment are affected? How long will it take? Do we have the internal resources and expertise for a seamless migration? What will upgrading the application cost?

Scenario 2: “We think we’ll be OK; my vendor said they will have new version in time.” It is true that some applications can simply be installed and run on a newer operating system, but the ability to function in another operating system is not enough. Each application’s PA-DSS validation must include testing for every platform. This means a vendor that had its application tested only on Windows XP needs a new assessment to test that application on, say, Windows 7.

My check of the PA-DSS list uncovered a number of validated applications with only Windows XP versions listed under Tested Platforms/Operating Systems. Therefore, although it may sound reassuring to hear that your old Windows XP POS can (possibly) run on Windows 7 or Windows 8, that fact alone is no guarantee that the version is or will be PA-DSS validated. Some questions for retailers in this scenario are: What are the vendor’s plans for PA-DSS validation? Can we see something in writing? Is the PA-QSA engaged or scheduled yet? How soon can we see the Implementation Guide, so we know what we are in for? How much will this cost?

Scenario 3: “We don’t know the impact yet, because we have a complicated POS environment.”