Final answer:
A Mandatory Access Control (MAC) model is used in an organization where access permissions are based on data labels and clearance levels. It is a rigid system that dictates access permissions through classification levels for both data and users.
Step-by-step explanation:
An organization that implements an access control model based on data labels assigned at different levels is using a Mandatory Access Control (MAC) model. In this system, permissions to access resources are based on the classification levels assigned to both the data and the users. For example, in a MAC model, data can be classified into various levels such as 'confidential', 'secret', or 'top secret', and users are granted access to this data only if they possess the appropriate clearance level.
The MAC model is characterized by its rigidity and the fact that users cannot share resources at will, as the permissions are enforced by the system, not by the owners of the information. This is in contrast to Discretionary Access Control (DAC), where the access control is determined by the owner of the resource.