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Understanding ACLs and Their Applications

Sep 5, 2025

Overview

This lecture covers Access Control Lists (ACLs), explaining their purpose, structure, and applications for both file systems and network security.

Access Control Lists (ACLs)

  • An Access Control List (ACL) defines permissions for objects such as files or folders.
  • ACLs are structured as tables or databases listing access rights for users or groups.
  • Each ACL is made up of multiple Access Control Entries (ACEs).
  • ACEs specify what actions (read, write, execute) are allowed or denied for a user or group on an object.

Network Security and ACLs

  • ACLs are used in network devices like routers, switches, and firewalls for security.
  • Network ACLs restrict access to hosts or services within a network.
  • They can be applied to both incoming and outgoing network traffic.
  • Network ACLs help enforce policies, restrict external system access, and prevent unauthorized outbound data transfers.

Key Terms & Definitions

  • Access Control List (ACL) — a table or database specifying access permissions for objects.
  • Access Control Entry (ACE) — an individual entry in an ACL defining a user or group's permissions.
  • File System ACL — an ACL applied to files, folders, or programs to control access.
  • Network ACL — an ACL used on network devices to control network traffic and access.

Action Items / Next Steps

  • Review examples of file system and network ACL configurations.
  • Prepare to identify and interpret ACLs on various operating systems and network devices.