Chapter 1 What’s New for FortiOS 5.0 : Security Features : Exempting IP addresses from IPS
  
Exempting IP addresses from IPS
IPS filters can be configured so that signatures are not applied to traffic from specific IP addresses. To exempt an IP address, a filter must be created with the Sensor Type set to Specify Signatures. Exempt IP can then be enabled and the necessary exemptions configured using Source and Destination IPs.
Figure 32: Exempting IP addresses from IPS