Chapter 15 Unified Threat Management for FortiOS 5.0 : Web filter : Overriding FortiGuard website categorization : Using Alternate Profiles : Identity or Address
  
Identity or Address
In either case what these override features do is, for specified users, user groups or IP addresses, allow sites blocked by Web Filtering profiles to be overridden for a specified length of time. The drawback of this method of override is that it takes more planning and preparation than the rating override method. The advantage is that once this has been set up, this method requires very little in the way of administrative overhead to maintain.
When planning to use the alternative profile approach keep in mind the following: In Boolean terms, one of the following "AND" conditions has to be met before overriding the Web Filter is possible
Based on the IP address:
The Web Filter profile must be specified as allowing overrides
AND the user's computer is one of the IP addresses specified
AND the time is within the expiration time frame.
While the conditions are fewer for this situation there is less control over who has the ability to bypass the filtering configured for the site. All someone has to do is get on a computers that is allowed to override the Web Filter and they have access.
Based on user or user group:
The Web Filter profile must be specified as allowing overrides
AND the policy the traffic is going through must be identity based
AND the user's credentials matches the identity credentials specified
AND the time is within the expiration time frame.
This method is the one most likely to be used as it gives more control in that the user has to have the correct credential and more versatile because the user can use the feature from any computer that uses the correct policy to get out on the Internet.