Which of the following security principles most likely requires validation before allowing traffic between systems?

Policy enforcement refers to the application of security policies to control access to resources based on predetermined rules. While it may involve validation, it does not inherently require verification of each individual request before allowing traffic, as Zero Trust architecture specifically dictates.

Authentication is the process of verifying the identity of a user or system before granting access. Although vital in the context of security, it is just one component of the broader Zero Trust framework, which emphasizes continuous validation and not merely initial authentication.

Confidentiality ensures that sensitive information is not disclosed to unauthorized users. While it is a critical security principle, it does not specifically focus on the validation of traffic between systems. Instead, it pertains more to the protection of data from unauthorized access rather than the processes governing traffic control.