An access control list (ACL) is a security measure used in computer systems and networks to regulate and control access rights or permission levels granted to users or entities. It is a fundamental method of enforcing security policies by defining the permissions on specific resources, such as files, directories, network ports, or network devices.
Implemented in various systems, including operating systems, routers, firewalls, and servers, an access control list serves as a set of rules or entries that determine what actions or operations are permitted or denied to users or groups. It typically consists of a list of entries, each containing a combination of criteria, such as source or destination IP addresses, protocols, port numbers, and user identities or group memberships.
Each entry in an ACL typically specifies a permit or deny action, effectively allowing or blocking access to the associated resource. When a user or entity requests access to a resource, the system compares the criteria of the ACL entries against the request, and if a match is found, the corresponding action is applied.
Access control lists provide granularity in access permissions, enabling administrators to customize and tailor access privileges based on specific requirements and security policies. By implementing ACLs, organizations can enhance the security of their systems, safeguard sensitive information, prevent unauthorized access, and manage user privileges effectively. They play a vital role in maintaining the confidentiality, integrity, and availability of resources in computer networks and systems.
