Which of the following is a method for protecting data from unauthorized access?

Zone boundary protection is a method for safeguarding data from unauthorized access by creating security boundaries around different network zones. This approach involves implementing firewalls, routers, and other security devices to control and monitor traffic between distinct zones with varying security levels. By establishing these zones, organizations can effectively manage access rights, enforce policies, and reduce the risk of security breaches.

Zone boundary protection focuses on preventing threats from easily moving across interconnected systems and thereby helps protect sensitive data from unauthorized users. It allows for a more structured and controlled environment where security measures can be tailored to specific zones containing critical assets.

In contrast, general-purpose person-to-person communication lacks any specific security measures and is not a suitable method for safeguarding data. Public key propagation, while useful for encryption and verification purposes, primarily focuses on secure communications rather than direct data protection. Cloud storage options may offer some level of security but depend heavily on the service provider's infrastructure and policies, making them less reliable as a standalone method for protecting data.