Access control matrix in Operating Systems - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an Access Control Matrix?

An Access Control Matrix is a table that shows which users (subjects) have what kind of access (permissions) to which resources (objects) in a system.

beginner

What are the main components of an Access Control Matrix?

The main components are subjects (like users or processes), objects (like files or devices), and the rights or permissions (like read, write, execute) that subjects have on objects.

beginner

How does an Access Control Matrix help in security?

It helps by clearly defining who can do what with each resource, preventing unauthorized access and protecting system resources.

intermediate

What is a limitation of using a full Access Control Matrix in real systems?

The matrix can become very large and sparse, making it inefficient to store and manage directly for systems with many users and resources.

intermediate

Name two common ways to implement Access Control Matrices in operating systems.

Access Control Lists (ACLs), which list permissions per object, and Capability Lists, which list permissions per subject.

What does an Access Control Matrix primarily represent?

A User passwords

B Network connections between computers

C File storage locations

D Permissions of subjects on objects

An Access Control Matrix shows which subjects have what permissions on which objects.

In an Access Control Matrix, what are 'subjects'?

A Resources like files or devices

B Users or processes that access resources

C Security policies

D Encryption keys

Subjects are entities like users or processes that request access to resources.

Which of the following is NOT a typical permission in an Access Control Matrix?

A Delete user account

B Write

C Read

D Execute

Deleting user accounts is usually managed by system policies, not typical object permissions.

Why is a full Access Control Matrix often not stored directly in systems?

A It is illegal to store

B It is too small to be useful

C It is too large and mostly empty

D It requires special hardware

The matrix can be very large and sparse, so storing it directly is inefficient.

Which method lists permissions per object rather than per subject?

A Access Control List (ACL)

B Capability List

C Encryption

D Firewall

ACLs list which subjects have permissions on a particular object.

Explain what an Access Control Matrix is and why it is important in operating systems.

Think about how a system controls who can do what with files or devices.

Describe two common ways to implement access control based on the Access Control Matrix concept.

One focuses on objects, the other on subjects.