What is the difference between mandatory and discretionary access control?

Mandatory Access Control (MAC) and Discretionary Access Control (DAC) are two different models used in computer security to regulate access to resources. Let's delve into the technical details of each:

  1. Mandatory Access Control (MAC):
    • Overview:
      • MAC is a security model in which access control decisions are primarily based on the security labels assigned to subjects (users or processes) and objects (resources such as files or devices).
      • The labels are typically hierarchical and indicate the sensitivity or classification level of the information.
    • Technical Aspects:
      • Labels: Each subject and object has a security label associated with it. These labels are often expressed as security clearances or classifications.
      • Access Decisions: Access decisions are made based on predefined rules and policies that consider the labels of both the subject and the object.
      • Enforcement: The system enforces access control by comparing the security labels and ensuring that the subject's label permits access to the object's label.
    • Example:
      • In a military setting, a user with a "Top Secret" clearance may have access to documents labeled as "Top Secret" but not to documents labeled as "Secret."
  2. Discretionary Access Control (DAC):
    • Overview:
      • DAC is a security model that allows owners of resources to have control over who can access those resources and what actions they can perform.
      • Access decisions are based on the identity of the requesting subject and the discretion of the resource owner.
    • Technical Aspects:
      • Access Control Lists (ACL): DAC is often implemented using Access Control Lists, where each resource has a list of users or groups and their corresponding permissions (read, write, execute).
      • Owner's Authority: The owner of a resource has the authority to grant or revoke access to other users or groups.
    • Example:
      • In a file system with DAC, a file owner may specify that User A has read and write permissions, while User B has only read permissions.

Key Differences:

  1. Control Authority:
    • MAC: Control is typically centralized, and access decisions are made by system administrators based on security policies.
    • DAC: Control is decentralized, and resource owners determine access permissions.
  2. Flexibility:
    • MAC: Less flexible, as access control is usually based on strict, predefined rules.
    • DAC: More flexible, as resource owners can dynamically change access permissions.
  3. Granularity:
    • MAC: Generally provides finer granularity in access control, especially in environments where data classification is crucial.
    • DAC: Provides granularity based on resource ownership but may not be as detailed in classifying data sensitivity.