Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, individual users are accountable for their own actions, which means they should use strong passwords, change them regularly, and not share them with anyone else. This is one of the requirements for ensuring that user accounts are properly managed and controlled.

Explanation
when a cryptographic key is retired and replaced with a new key, the new key must have an appropriate strength for its intended use, which means it should have a sufficient length and complexity to resist brute-force attacks. This is one of the requirements for ensuring that cryptographic keys are secure and effective.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, visitors are escorted at all times within areas where cardholder data is processed or maintained, visitor badges are identical to badges used by onsite personnel, visitor log includes visitor name, address, and contact phone number, visitors retain their identification (for example a visitor badge) for 30 days after completion of the visit. These are some examples of procedures that must be included in an organization’s procedures for managing visitors who access in-scope systems where cardholder data is processed or maintained.

Explanation
classifying media that contains cardholder data is intended to ensure that media is property protected according to the sensitivity of the data it contains, which means it should be marked with labels or tags that indicate its level of confidentiality or integrity. This is one of the requirements for ensuring that media containing cardholder data is properly labeled.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, a different certificate is assigned to each individual user account, and certificates are not shared. This is one of the requirements for preventing unauthorized access to cardholder data using digital certificates.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, internal vulnerability scans must be performed after a significant change in any component or configuration that affects cardholder data or payment processing systems. This is one of the requirements for identifying and mitigating vulnerabilities that could compromise cardholder data.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, private or secret keys must be encrypted, stored within an SCD or stored as key components. This is one of the requirements for ensuring secure encryption and authentication.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, an internal NTP server that provides time services to the cardholder data environment is in scope for PCI DSS if it stores processes or transmits cardholder data, regardless of whether it provides authentication services to systems in the DMZ or not. This is one of the requirements for preventing unauthorized access to cardholder data using time services.

Explanation
The customized approach is a new option in PCI DSS v4.0 that allows entities to use alternate security controls or new technologies that meet the PCI DSS Customized Approach Objective for a requirement1. The customized approach requires the entity to complete and document a Controls Matrix and a Targeted Risk Analysis (TRA) for each customized control, and to provide this documentation to the assessor2. The assessor’s role is to review the documentation, assess the customized control, and verify that the customized approach was correctly followed3. The assessor must also document the assessment of the customized control in the Report on Compliance (ROC), using the ROC Template provided by PCI SSC4. Therefore, the correct answer is option B.
The other options are not true regarding the role of the assessor in the customized approach. Option A is not true because the assessor does not need another assessor to verify the TRA, as the assessor is responsible for reviewing and validating the TRA as part of the assessment process3. Option C is not true because the assessor can and must assess the control and the documentation, as well as document the work on the customized control in the ROC34. Option D is not true because the assessor is allowed to assist the entity with the completion of the Controls Matrix or the TRA, as long as the assessor does not design, develop, or implement the customized control for the entity5. References:
PCI DSS v4.0: Is the Customized Approach Right For Your Organization?
PCI DSS v4.0: Roles and Responsibilities for the Customized Approach
PCI DSS v4.0 Report on Compliance Template
PCI DSS v4.0
PCI DSS v4.0: Customized Approach Explained

Explanation
According to the glossary, bespoke and custom software describes software developed by an entity for its own use, which means it should not be shared with other entities or sold or transferred without proper authorization. This is one of the requirements for ensuring that bespoke and custom software meets all the security standards and controls defined in Appendix E of the PCI DSS v3.2.1 Quick Reference Guide1.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, the assessor must derive testing procedures and document them in Appendix E of the ROC. This is one of the requirements for ensuring that testing procedures are defined and documented.

Explanation
According to the PCI DSS v3.2.1 Quick Reference Guide1, the database server should be relocated so that it is not accessible from untrusted networks. This is one of the requirements for protecting cardholder data in transit and at rest.

Explanation
when disk encryption is used to protect account data, access to the disk encryption must be managed independently of the operating system access control mechanisms, which means it should not be affected by changes in the operating system settings or permissions. This is one of the requirements for ensuring that disk encryption is secure and effective.

Explanation
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. Virtual LANs (VLANs) are one example of such a security control, as they can create logical subnetworks that separate different types of traffic and restrict access between them3.
Therefore, the correct answer is option C.
The other options are not true regarding the scenario that describes segmentation of the cardholder data environment (CDE) for the purposes of reducing PCI DSS scope. Option A is not true because routers that monitor network traffic flows between the CDE and out-of-scope networks are not sufficient to isolate the CDE, as they do not prevent or limit the traffic flows. Option B is not true because firewalls that log all network traffic flows between the CDE and out-of-scope networks are not sufficient to isolate the CDE, as they do not block or filter the traffic flows. Option D is not true because a network configuration that prevents all network traffic between the CDE and out-of-scope networks is not realistic or feasible, as some traffic may be necessary for business or legal reasons, such as payment processing, reporting, or auditing. References:
Network Segmentation – PCI Security Standards Council
Guidance for PCI DSS Scoping and Network Segmentation
VLANs and PCI Compliance: What You Need to Know

Explanation
According to requirement 4, PAN must be protected with strong cryptography for transmission over private wireless networks, which means it should use encryption techniques such as WEP, WPA, WPA2, or TLS/SSL to prevent unauthorized access or interception of cardholder data over wireless networks. This is one of the requirements for ensuring that PAN is protected from unauthorized access or interception.

Explanation
One of the best practices for hardening a firewall is to disable any firewall functions that are not needed in production, such as unused services, ports, protocols, or features. This reduces the attack surface and minimizes the potential for exploitation. According to the PCI Card Production Logical Security Requirements, section 3.2.1, “The firewall must be configured to deny all traffic by default and allow only traffic that is explicitly required for the card production environment.” Furthermore, section 3.2.2 states, “The firewall must be configured to block all unnecessary services, ports, protocols, and IP addresses.” References: PCI Card Production Logical Security Requirements, Card Production Security Assessor – Logical – Credly

Explanation
Hashing is a form of one-way encryption that transforms a data element into a unique fixed-size data element (hash value) without a way to get the original data element from the hash value1. Truncation is a method of rendering the full PAN unreadable by permanently removing a segment of the PAN data2. PCI DSS Requirement 3.4 states that entities must render the PAN unreadable wherever it is stored, using any of the following methods: one-way hashes based on strong cryptography, truncation, index tokens and pads, or strong cryptography with associated key-management processes and procedures3. However, PCI DSS Requirement 3.4e also states that if hashed and truncated versions of the same PAN are present in the environment, additional controls must be in place to ensure that the hashed and truncated versions cannot be correlated to reconstruct the original PAN3. This is because if an attacker obtains both the hashed and truncated versions of the same PAN, they may be able to use a brute-force or dictionary attack to guess the original PAN by hashing and truncating different PAN values until they find a match4. Therefore, the correct answer is option A.
The other options are not true regarding the presence of both hashed and truncated versions of the same PAN in an environment. Option B is not true because PCI DSS does not require the hashed version of the PAN to be also truncated, although it is a recommended best practice to further reduce the risk of exposing the original PAN5. Option C is not true because PCI DSS does not require the hashed and truncated versions to be correlated, as this would defeat the purpose of rendering the PAN unreadable and increase the risk of exposing the original PAN. Option D is not true because PCI DSS does not prohibit the presence of both hashed and truncated versions of the same PAN in the same environment, as long as additional controls are in place to prevent the reconstruction of the original PAN. References:
Protect hashed CardHolder Data according to PCI DSS 3.4 – Advantio
PCI DSS Truncation Rules and Guidelines – Truvantis
PCI DSS v3.2.1
Storing Card Numbers using hashed and truncated version of PAN
pci dss – Credit card data security – hashing, truncation and encryption – Information Security Stack Exchange