Access Control Model: An "access control model" is a framework that outlines how access rights and permissions are managed and assigned in a computer system or network. It dictates how users and systems can interact with and access resources, such as files, applications, or network segments. Common models include discretionary access control (DAC), where resource owners decide on access rights; mandatory access control (MAC), which relies on a centralized policy to determine access based on user classifications and security clearances; and role-based access control (RBAC), where access is granted based on the roles and responsibilities within an organization. These models are essential for ensuring that only authorized individuals or systems can access sensitive information, thereby maintaining security and protecting data integrity.

History: The history of access control models is closely tied to the evolution of computer and network security. Initially, in the early days of computing, security was a secondary concern, with the main focus on functionality and performance. However, as computers started to be used for sensitive and classified information, particularly in military and government applications, the need for robust security mechanisms became evident. This led to the development of early access control models. One of the first formal models was the Mandatory Access Control (MAC) model, developed in the 1970s, influenced heavily by military security requirements where data classification and clearance levels were crucial. Around the same time, Discretionary Access Control (DAC) emerged, offering a more flexible approach by allowing the resource owner to control access.