| Securing and controlling access to LANs and WANs is a critical part of preventing unauthorized access to your network. Once authenticated, CiscoSecure" ACS helps ensure network security and log access. uses Terminal Access Controller Access Control System (TACACS+) and Remote Authentication Dial In User Service (RADIUS) to provide security and tracking provides Authentication, Authorization, and Accounting AAA operates in the client server model; the network access server is the client and the CiscoSecure ACS is the server.