Which of these is a form of data protection specified by PCI DSS?

Data encryption is a critical form of data protection specified by PCI DSS because it ensures that sensitive customer data, such as credit card numbers and personal information, is transformed into a secure format that cannot be easily read or accessed by unauthorized individuals. The PCI DSS emphasizes the importance of protecting cardholder data both in transit and at rest. By employing encryption, organizations can significantly reduce the risk of data breaches, as even if data is intercepted, it remains secure and unreadable without the appropriate decryption keys.

While other forms of protection, such as biometrics, firewall protection, and physical security audits, play important roles in an overall security strategy, they do not specifically address the critical need for safeguarding sensitive data through encryption. Each of these elements could support the security framework but encryption directly targets the protection of data itself, aligning perfectly with PCI DSS requirements.