Chapter 3 Authentication for FortiOS 5.0 : Agent-based FSSO : Troubleshooting FSSO : FortiGate performance is slow on a large network with many users : Solution
  
Solution
Add users to the Ignore User list. This a best practice for admin accounts whose logon information will not be sent to the FortiGate unit. This is useful for automated accounts that may logon many times. Examples of accounts in this category include:
IIS services
AV
other system accounts
For more information on configuring the Ignore users list, see “Configuring the Ignore User List”.