Chapter 6 Deploying Wireless Networks for FortiOS 5.0 : Introduction to wireless networking : Authentication
  
Authentication
Wireless networks usually require authenticated access. FortiOS authentication methods apply to wireless networks the same as they do to wired networks because authentication is applied in the firewall policy.
The types of authentication that you might consider include:
user accounts stored on the FortiGate unit
user accounts managed and verified on an external RADIUS, LDAP or TACACS+ server
Windows Active Directory authentication, in which users logged on to a Windows network are transparently authenticated to use the wireless network.
This Wireless chapter of the FortiOS Handbook will provide some information about each type of authentication, but more detailed information is available in the Authentication chapter.
What all of these types of authentication have in common is the use of user groups to specify who is authorized. For each wireless LAN, you will create a user group and add to it the users who can use the WLAN. In the identity-based firewall policies that you create for your wireless LAN, you will specify this user group.
Some access points, including FortiWiFi units, support MAC address filtering. You should not rely on this alone for authentication. MAC addresses can be “sniffed” from wireless traffic and used to impersonate legitimate clients.