Segmentation is a method of isolating system components that store, process, or transmit cardholder data from systems that do not, by using security controls such as firewalls, routers, switches, or other devices1. Segmentation can reduce the scope of the cardholder data environment (CDE) and thus reduce the scope of the PCI DSS assessment, as only the systems and networks within the CDE or connected to the CDE are subject to PCI DSS requirements2. However, segmentation is not mandatory for PCI DSS compliance, and it is the responsibility of the entity to define and document the scope of their CDE and the segmentation controls they use2.

The assessor’s role is to verify the scope of the CDE and the effectiveness of the segmentation controls, as specified in PCI DSS Requirement 11.3.43. The assessor must verify that the segmentation controls are configured properly and functioning as intended, and that they allow only necessary traffic into the CDE. The assessor must also perform penetration testing on the segmentation controls at least annually and after anychanges to the segmentation methods, to confirm that there are no exploitable vulnerabilities that could allow an attacker to access the CDE from out-of-scope systems3. Therefore, the correct answer is option D.

The other options are not true regarding the role of the assessor in verifying segmentation for PCI DSS. Option A is not true because the assessor must verify not only that the segmentation controls allow only necessary traffic into the CDE, but also that they are configured properly and functioning as intended, as stated in option D. Option B is not true because the assessor does not need to verify that the payment card brands have approved the segmentation, as PCI DSS does not require such approval, although the payment card brands may have their own policies and procedures for segmentation that the entity must follow2. Option C is not true because the assessor does not need to verify that approved devices and applications are used for the segmentation controls, as PCI DSS does not mandate the use of specific devices or applications for segmentation, although it requires the entity to use industry-accepted and strong methods for segmentation2. References:

Network Segmentation - PCI Security Standards Council

Guidance for PCI DSS Scoping and Network Segmentation

PCI DSS v3.2.1