Access Control List (ACL)

An Access Control List (ACL) is a security mechanism used in computer systems and networks to control and manage access to resources, such as files, folders, directories, or network services. It specifies the permissions and privileges that are granted or denied to individual users or groups of users for accessing and interacting with these resources.

ACLs are commonly used to enforce the principle of least privilege, which means granting users or processes only the minimum level of access necessary to perform their tasks while preventing unauthorized access and potential security breaches.

An ACL typically consists of a list of entries, each of which corresponds to a specific user, group, or entity and specifies the permissions associated with that entity's access to a particular resource. These permissions can include actions such as read, write, execute, delete, and more. ACLs are closely related to file systems and network services, where they play a crucial role in maintaining security and managing user access.

There are two main types of ACLs:

1. Discretionary Access Control Lists (DACLs): These are managed by the owner of the resource. The owner can specify which users or groups have access to the resource and what level of access they have.

2. System Access Control Lists (SACLs): These are used to log specific access events on a resource. They allow administrators to track who accessed a resource and what actions they performed.

ACLs can become quite complex when managing permissions for multiple users and groups, so proper planning and administration are crucial to ensure the security and integrity of the system.