Fortinet Fortigate-5000 series - Web Filter; Order of web filtering; How web filtering works

Web Filter Order of web filtering
FortiGate Version 3.0 MR4 Administration Guide
01-30004-0203-20070102 361
Web Filter
The three main sections of the web filtering function, the Web Filter Content
Block, the URL Filter, and the FortiGuard Web filter, interact with each other in
such a way as to provide maximum control and protection for the Internet users.
This section contains the following topics:
• Order of web filtering
• How web filtering works
• Web filter controls
• Content block
• URL filter
• FortiGuard - Web Filter
Order of web filtering
Web filters are applied in a specific order:
1 URL Exempt (Web Exempt List)
2 URL Block (Web URL Block)
3 URL Block (Web Pattern Block)
4 FortiGuard Web Filtering (Also called Category Block)
5 Content Block (Web Content Block)
6 Script Filter (Web Script Filter)
7 Antivirus scanning
The URL filter list is processed in order from top to bottom. (In FortiOS v2.80 the
URL filter is processed as an unordered list.) An exempt match stops all further
checking including AV scanning. An allow match exits the URL filter list and
checks the other web filters.
Local ratings are checked prior to other FortiGuard Web Filtering categories.
The FortiGate unit applies the rules in this order and failure to comply with a rule
will automatically block a site despite what the setting for later filters might be.
How web filtering works
The following information shows how the filters interact with each other and how
to use them to your advantage.
The first section, the URL exempt and block filters, will allow you to decide what
action to take for specific addresses. For example, if you want to exempt
www.google.com from being scanned, you can add it to the URL exempt list. Then
no web filtering or virus scanning will be taken to this web site.