Access Controls Part 1: Computer Security Lectures 2014/15 S2

Summary

The video script delves into the critical concept of access controls, which are mechanisms that regulate what users and programs can do within a computer system. It emphasizes the significance of access controls for security, highlighting the importance of authentication before authorization. The lecture distinguishes between physical and digital access controls, focusing on the latter. It outlines the necessity of a security policy, the trusted computing base, and the role of the reference monitor in mediating access to resources. The script also explains the access control matrix, a theoretical model for describing security states, and contrasts it with real-world implementations like access control lists (ACLs) and capabilities. The discussion further explores various access control models, including mandatory access control, discretionary access control, and role-based access control. It concludes with practical advice on using access controls, particularly the risks of operating as an administrator and the benefits of user access control in modern operating systems.

Takeaways

• 🔒 **Access Controls** are critical for computer security, determining what users and programs can do within a system.
• 🛡️ **Authentication** is the first step, confirming the identity of a user or process before access control can be enforced.
• 📜 **Authorization** follows authentication, defining what actions an authenticated subject is permitted to perform.
• 🏢 **Physical Security** can be thought of as access control in the physical world, like using a badge to enter a room.
• 📐 **Digital Access Control** is analogous to physical security, but it applies to digital resources and processes.
• 📋 **Access Control Matrix** is a theoretical model that details every possible access permission in a system, though not practical for large systems.
• 🔑 **Trusted Computing Base (TCB)** includes all the software and hardware responsible for enforcing security policy.
• 🚪 **Complete Mediation** ensures that all access to resources is controlled and that there are no backdoors or unguarded paths.
• 📁 **Subjects and Objects** are fundamental to access control; subjects are the entities performing actions, and objects are the resources being acted upon.
• 📝 **Security Context** includes the identity and related information assigned to each subject, which informs access decisions.
• 📊 **Access Control Policies** can be formal or informal and are defined by an organization to ensure confidentiality, integrity, and availability of information.
• 🏗️ **Access Control Mechanisms** are the tools or technologies that enforce the policy, such as firewalls or access control lists (ACLs).
• 📈 **Role-Based Access Control (RBAC)** assigns permissions based on roles within an organization, allowing for flexible and manageable access control.
• 🤝 **Discretionary Access Control (DAC)** allows users to control access to their own files, which is common in consumer operating systems like Windows and Linux.
• 📍 **Mandatory Access Control (MAC)** is where access is strictly defined and enforced by a central authority, often used in military or government settings.

Q & A

What is the primary purpose of access controls in computer systems?

Access controls in computer systems are designed to restrict what people and programs are allowed to do, playing a crucial role in ensuring security.

How does physical security relate to the concept of access controls?

Physical security involves access controls like doors, gates, and badges that keep unauthorized individuals out of certain areas, similar to how digital access controls restrict access to digital resources.

What is the difference between authentication and authorization in the context of access controls?

Authentication is the process of verifying the identity of a user or system, while authorization is the step that follows, determining what actions the authenticated subject is permitted to perform.

What is the concept of a 'subject' in access control?

In access control, a 'subject' refers to the person or program that is trying to perform an action or access a resource, such as a file or another process.

What is an 'object' in the context of access control?

An 'object' in access control is typically a static resource like a file or a process that a subject might attempt to access or interact with.

Why is complete mediation important in access control systems?

Complete mediation ensures that all access to resources is consistently checked against the security policy, preventing unauthorized access through unguarded pathways or methods.

What is the Trusted Computing Base (TCB)?

The TCB represents all the software, hardware, and components that work together to enforce the security policy, including critical parts like the operating system kernel.

How does the concept of an Access Control Matrix help in understanding security policies?

An Access Control Matrix is a theoretical construct that provides a comprehensive table detailing every possible access permission, helping to conceptualize and analyze security policies.

What are the two main types of access control models discussed in the script?

The two main types of access control models are nondiscretionary access control (also known as mandatory access control) and discretionary access control.

How does discretionary access control differ from mandatory access control?

Discretionary access control allows users to own files and decide who can access them, whereas mandatory access control is enforced by a central authority that dictates access rules for all users without their input.

What is the role of a reference monitor in access control?

A reference monitor is a concept that ensures every access to a resource, like a file, is mediated by a central authority (like an operating system kernel) that checks if the access is allowed according to the security policy.

Why is it recommended not to use an administrator account for daily tasks on a computer system?

Using an administrator account for daily tasks can lead to accidental harmful actions due to the high level of permissions, potentially causing irreversible damage to the system.