What is an Access Control List (ACL)? Comprehensive Guide

An ACL or Access Control List is a mechanism for controlling and managing access to resources on a computer system or network. It is essentially a list of permissions or rules that define what actions by users or groups are allowed or denied on a particular resource.

In computer systems, resources can include files, directories, network resources, or even individual functions or features in a software application. With ACLs, administrators can define access permissions for these resources. This allows only authorized users to be granted access to certain information and permission to perform certain actions.

ACLs consist of access control records that define a combination of identifiers and corresponding permissions (read, write, execute, delete, etc.).

There are two types of ACLs:

• Discretionary ACLs or DACs are commonly used in file systems to allow the owner of a resource to control who has access to it. DACs provide flexibility because the owner of a file or directory can assign permissions to specific users or groups.
• Mandatory ACLs or MACs are used in high-security environments where a system administrator or security policy establishes access control to resources. MAC is used in government or military environments where access permissions are set by the system.

ACLs provide a high level of security, limits unauthorized access to sensitive data and critical resources. They allow administrators to implement the principle of least privilege by granting users only those permissions necessary to perform their tasks.