FortiOS supports two different types of authentication based on your situation and needs.

Security policy authentication, or identity-based policies, is easily applied to all users logging on to a network, or network service. For example if a group of users on your network such as the accounting department who have access to sensitive data need to access the Internet, it is a good idea to make sure the user is a valid user and not someone trying to send company secrets to the Internet. Security policy authentication can be applied to as many or as few users as needed, and it supports a number of authentication protocols to easily fit with your existing network.

VPN authentication can be for both the remote VPN device as well as the VPN users. VPNs are used to communicate with locations outside the company network as if they were part of the company network. This level of trust, once a VPN is established, is easily established with authentication to verify the remote user is in fact a valid user. In this situation without authentication, anyone malicious or otherwise could connect to the company network with potentially full access.