Which of the following best describes explicit and implicit deny in access control?

The choice that correctly describes explicit and implicit deny in access control is that explicit deny overrides all permissions, while implicit deny applies where no permissions are assigned.

Explicit deny refers to a specific permission setting that explicitly disallows access to a resource. When a user is explicitly denied access, that denial takes precedence over any other permissions assigned to that user, whether they are allow or deny permissions. This ensures a strong control mechanism where certain users or roles can be prevented from accessing critical resources, regardless of any permissions that may be granted.

Implicit deny operates on the principle that if a permission is not explicitly granted to a user, then they are denied access by default. This means that in environments where permissions are carefully controlled, if a user has not been given permission to access a resource, they will automatically be denied that access. Implicit deny acts as a safety net to prevent unauthorized access when there is ambiguity or lack of defined permissions.

The distinction between these two mechanisms is crucial for establishing secure access control policies, ensuring that security is reinforced by denying all by default unless explicitly permitted.