Best Practices for PCI DSS Scoping & Segmentation in Modern Network Architectures

Maintaining Payment Card Industry Data Security Standard (PCI DSS) compliance is becoming more difficult as businesses adopt modern network infrastructures like cloud-environments, Zero Trust models, and virtual networks. Proper scoping and segmentation are essential to minimize risk and to protect cardholder data. In this article, we'll explore some key strategies to implement in order to achieve and maintain PCI DSS compliance.

What is PCI DSS Scoping and Segmentation?

PCI DSS scoping involves identifying which parts of your network handle or impact cardholder data and, therefore, must comply with PCI DSS controls. Segmentation, on the other hand, is the practice of isolating systems that handle cardholder data from those that do not.

By segmenting networks, you reduce the overall PCI DSS scope, which simplifies PCI compliance and reduces risk. This is especially important in today's modern architectures where cloud services, hybrid environments, and virtualized networks complicate how data flows and is stored. Ensuring proper segmentation is one of the layers of a “defense in depth” strategy to help safeguard access to sensitive data. 

Here are some key practices for scoping and segmentation:

• Map your cardholder data environment (CDE): Clearly define where you receive, transmit, manipulate and store cardholder data. Then understand the systems and business processes that support these activities.
• Segment your network: Isolate systems that handle cardholder data from other parts of the network. This reduces the number of systems that will be validated for PCI DSS compliance scope.
• Regularly review segmentation controls: Conduct frequent penetration testing to ensure that your internal and external segmentation configurations remain effective over time.
• Note that segmentation is not a requirement of PCI DSS, however without segmentation, there is potential that your entire environment and your third party’s environment need to be reviewed and assessed.

Applying Zero Trust Architecture Principles

The easiest way to understand Zero-Trust is that you are no longer focused on the network that controls access, but rather access to the data. Essentially there is no trust between any internal or external factors—whether this be in the form of users, applications or management systems that access your data. In a Zero Trust network, it is important to be more granular on the design of segmentation controls in order to control access to sensitive data. Notably, Zero Trust environments shift the focus from the perimeter defenses to granular, identity-based access controls. This reduces the risk of attacks by limiting unauthorized access within the network itself.

Here are some important factors for implementing ZeroTrust:

• Micro-segmentation: Divide your network into small, isolated zones where access is granted on a per-transaction or per-session basis. Each segment should be independently verified.
• Implement a Continuous Verification Process: Apply robust identity and access management (IAM) policies to continuously confirm and verify the identity of users, applications, and devices before granting access to CDE.
• Impose Least Privilege Access: Ensure that users only have the minimum access needed to perform their roles. This reduces the risk of unauthorized access to cardholder data.

Addressing Hybrid Environments

Hybrid environments are a combination of on-premise infrastructure and cloud-based services. What is great about this setup is that it allows for more flexibility, but it can also lead to inconsistencies when applying security controls. This is especially true when managing PCI DSS scope across both environments. 

Here are our tips for navigating this:

• Consistent controls: Apply consistent security policies, such as encryption, authentication, and monitoring across both cloud and on-premise environments.
• Build data flow diagrams: Create clear detailed diagrams that map out how data flows between the on-premise and cloud environments.
• Have a unified Identity and Access Management (IAM) solution: Use IAM solutions that cover both cloud and on-premise systems, ensuring seamless enforcement of access controls and monitoring across the entire hybrid infrastructure.

Managing Segmentation in Virtualized Networks

Network virtualization technologies and service meshes allow for greater scalability and flexibility but also add complexity to segmentation efforts. Keep in mind that segmentation is applied at both the network and application levels in a virtualized network environment. This is to ensure that sensitive systems remain isolated. 

Here is a look at some of the key practices for managing segmentation in virtualized networks:

• Use software-defined segmentation (SND): Unlike traditional segmentation controls like firewalls and routers, in the cloud software is used to create virtual “appliances” that perform similar functions. SDN centralizes control over network traffic, allowing administrators to create virtual segments that isolate sensitive systems from others. This is essential in environments where different applications and services share the same physical infrastructure.
• Service mesh implementation: Service meshes provide an additional layer of segmentation by controlling communication between microservices. Use policies within the service mesh to enforce security rules at the application layer, ensuring that only authorized services can communicate with one another.
• Granular access control: Leverage the fine-grained access controls available in SDN and service mesh technologies to limit access between in-scope and out-of-scope systems.

Importance of Penetration Testing for Segmentation

Penetration testing is a crucial part of maintaining PCI DSS compliance. Why? It helps verify that your segmentation controls are working as intended and that no unintended connections exist between in-scope and out-of-scope systems. 

Here are a few best practices to keep in mind:

• Conduct comprehensive testing: Go beyond a simple port scan. Include testing for potential weaknesses in orchestration layers, virtualized environments, and network configurations.
• Multi-cloud and hybrid considerations: In multi-cloud and hybrid environments, penetration testing should include scenarios where data flows between different environments to ensure that segmentation boundaries are maintained.
• Continuous validation: Regular testing is crucial, as network configurations in cloud and hybrid environments are constantly changing. Implement automated tools to continuously monitor and validate segmentation controls.

How Control Gap Can Help with PCI DSS Scoping and Segmentation

Our team offers expert PCI DSS compliance solutions, ensuring that your organization's segmentation and scoping strategies are optimized for modern network environments. From multi-cloud to Zero Trust and hybrid infrastructures, our professionals can help you streamline your compliance efforts and reduce your PCI DSS scope, minimizing costs and risks. Connect with our team of professionals today to learn how we can help.