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Discretionary and Mandatory Access Control

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Summary

PDF p.92

Access control models determine how authenticated users receive rights and permissions on networks, computers, and data. Discretionary Access Control (DAC) is based on resource ownership, while Mandatory Access Control (MAC) is based on security clearance levels.

In plain words

Supplementary — not from your PDF

In discretionary access control (DAC) the owner of a file decides who can use it; Windows and Linux work this way by default. In mandatory access control (MAC) the system decides using labels and clearances that users can't change.

Detailed explanation

PDF p.92
  • Discretionary Access Control (DAC)
    • Definition: Based on the primacy of the resource owner, who has full control over the resource and its access control list (ACL).
    • Flexibility: Highly flexible and widely implemented in UNIX/Linux distributions and Microsoft Windows.
    • Weaknesses: Difficult to enforce centralized security policies and vulnerable to insider threats and compromised accounts.
  • Mandatory Access Control (MAC)
    • Definition: Based on security clearance levels, with each object given a classification label and each subject granted a clearance level.
    • Operation: Subjects can read objects at their clearance level or below.
    • Rules: Nondiscretionary and cannot be changed by any subject account.
    • Compartment-Based Access: Adds flexibility by allowing access based on both classification and compartment (e.g., Secret and HR).
    • Write Up, Read Down: Users with high clearance cannot write to low-clearance documents to prevent data leakage.

Important terms

taken from the text above
Discretionary Access Control (DAC)
Based on the primacy of the resource owner, who has full control over the resource and its access control list (ACL).
Flexibility
Highly flexible and widely implemented in UNIX/Linux distributions and Microsoft Windows.
Weaknesses
Difficult to enforce centralized security policies and vulnerable to insider threats and compromised accounts.
Mandatory Access Control (MAC)
Based on security clearance levels, with each object given a classification label and each subject granted a clearance level.
Rules
Nondiscretionary and cannot be changed by any subject account.
Compartment-Based Access
Adds flexibility by allowing access based on both classification and compartment (e.g., Secret and HR).
Write Up, Read Down
Users with high clearance cannot write to low-clearance documents to prevent data leakage.
DAC Discretionary Access Control MAC Mandatory Access Control

Examples & real-world scenarios

Supplementary — not from your PDF
  • DAC: you share a document with a colleague.
  • MAC: a 'Secret' clearance can read Secret and lower, but not Top Secret.
  • Compartments: 'Secret + HR' access.

Scenario

A contractor is added to a project folder by the folder's owner without IT knowing. That's DAC's flexibility, and its weakness for central control.

Common mistakes

Supplementary — not from your PDF
  • Reading 'Write Up, Read Down' as a mistake. It lists what's allowed, which is the same rule as 'no read up, no write down'.
  • Thinking MAC labels can be changed by the data owner.

Practical skills

Supplementary — not from your PDF
  • Decide whether a scenario describes DAC or MAC.

What I should remember

Key Points PDF p.92
  • Discretionary Access Control (DAC)
    • Resource Ownership: Owner controls access.
    • Flexibility: Highly flexible, widely used.
    • Weaknesses: Hard to enforce policies, vulnerable to insider threats.
  • Mandatory Access Control (MAC)
    • Security Clearance: Based on classification labels and clearance levels.
    • Nondiscretionary Rules: Cannot be changed by users.
    • Compartment-Based Access: Adds flexibility.
    • Write Up, Read Down: Prevents data leakage.