What is the primary purpose of installing a firewall in an environment subject to PCI compliance?

• A. To block all external access regardless of policy.
• B. To protect cardholder data from unauthorized access.
• C. To encrypt all data at rest automatically.
• D. To detect all zero-day exploits instantly.

Answer: (B)

A firewall in a PCI environment is there to protect cardholder data by controlling which devices and services can communicate with systems that store, process, or transmit payment card data. It enforces access controls at network boundaries and between segments, blocking unauthorized traffic and allowing only policy-approved connections, which helps meet PCI DSS requirements to safeguard cardholder data. It’s not about encrypting data at rest—that’s a separate measure—and it doesn’t guarantee zero-day exploit detection, which requires additional security controls. It also isn’t meant to blanket-block all external access regardless of policy; it enforces the defined access rules to minimize exposure.