Which principle guarantees that a user will not gain unauthorized access to resources?

The principle that guarantees a user will not gain unauthorized access to resources is the implicit deny concept. This principle states that unless a user's access is explicitly granted to a resource, they are denied access by default. This approach is foundational in access control models as it emphasizes security by ensuring that permissions are not given freely. This means that any action or resource not explicitly permitted is automatically blocked, thus preventing unauthorized access and reducing the risk of accidental or malicious breaches.

This principle is particularly valuable in environments where it is crucial to protect sensitive information, as it establishes a strong baseline of security. By ensuring all access is denied unless specifically allowed, organizations can better manage risks and maintain control over who can access critical systems and data.