Which of the following would be the best way to block unknown programs from executing?

An application allow list (or whitelist) is the most effective method for blocking unknown programs because it explicitly defines which applications are permitted to run. Any program not on this approved list is automatically blocked, providing a strong security posture against malware and unauthorized software. Access control lists (ACLs) manage permissions for users and groups on resources, not specifically program execution. A host-based firewall primarily controls network traffic in and out of a device, not the execution of local programs. A Data Loss Prevention (DLP) solution focuses on preventing sensitive data from leaving the organization, not on blocking unknown program execution.