Access Control Mechanism (ACM) definition in Computer Security terms:
Definition(s): Security safeguards (i.e., hardware and software features, physical controls, operating procedures, management procedures, and various combinations of these) designed to detect and deny unauthorized access and permit authorized access to an information system.
Source(s): CNSSI 4009-2015
The logical component that serves to receive the access request from the subject, to decide, and to enforce the access decision.
Source(s): NIST SP 800-162
reference: CSRC Glossary