Chapter 10 Install and System Administration for FortiOS 5.0 : Basic Administration : Administrators : Security Precautions : Disable interfaces
  
Disable interfaces
If any of the interfaces on the FortiGate unit are not being used, disable traffic on that interface. This avoids someone plugging in network cables and potentially causing network bypass or loop issues.
To disable an interface - web-based manager
1. Go to System > Network > Interface.
2. Select the interface from the list and select Edit.
3. For Administrative Access, select Down.
4. Select OK.
To disable an interface - CLI
config system interface
edit <inerface_name>
set status down
end
See Also
Security Precautions
Passwords
 
Disable admin services
Disable the console interface
Disable interfaces
SSH login time out
Administrator lockout
Idle time-out
Administrative ports
Change the admin username and password