Web content filter

You can control access to web content by blocking webpages containing specific words or patterns. This helps to prevent access to pages with questionable material. You can specify words, phrases, patterns, wildcards, and regular expressions to match content on webpages. You can use multiple web content filter lists and select the best one for each web filter profile. The maximum number of web content patterns in a list is 5000.

When configuring a web content filter list, the following patterns are available:

Web content pattern type	Description
Wildcard	Use this setting to block or exempt one word or text strings of up to 80 characters. You can also use wildcard symbols such as ? or * to represent one or more characters. For example, a wildcard expression forti*.com matches fortinet.com and fortiguard.com. The * represents any character appearing any number of times.
Regular expression	Use this setting to block or exempt patterns of regular expressions that use some of the same symbols as wildcard expressions, but for different purposes. In regular expressions, * represents the character before the symbol. For example, forti*.com matches fortiii.com but not fortinet.com or fortiice.com. In this case, the symbol * represents i appearing any number of times.

Content evaluation

The web content filter scans the content of every webpage that is accepted by a firewall policy. The system administrator can specify banned words and phrases and attach a numerical value (or score) to the importance of those words and phrases. When the web content filter scan detects banned content, it adds the scores of banned words and phrases found on that page. If the sum is higher than a threshold set in the web filter profile, the FortiGate blocks the page.

The default score for web content filter is 10 and the default threshold is 10. This means that by default, a webpage is blocked by a single match. These settings can only be configured in the CLI.

Banned words or phrases are evaluated according to the following rules:

• The score for each word or phrase is counted only once, even if that word or phrase appears many times in the webpage.

• The score for any word in a phrase without quotation marks is counted.

• The score for a phrase in quotation marks is counted only if it appears exactly as written.

The following table is an example of how rules are applied to the webpage contents . For example, a webpage contains only this sentence:

The score for each word or phrase is counted only once, even if that word or phrase appears many times in the webpage.

Banned pattern	Assigned score	Score added to the sum for the entire page	Threshold score	Comment
word	20	20	20	Appears twice but is only counted once. The webpage is blocked.
word phrase	20	40	20	Each word appears twice but is only counted once, giving a total score of 40. The webpage is blocked.
word sentence	20	20	20	word appears twice and sentence does not appear, but since any word in a phrase without quotation marks is counted, the score for this pattern is 20. The webpage is blocked.
"word sentence"	20	0	20	This phrase does not appear exactly as written. The webpage is allowed.
"word or phrase"	20	20	20	This phrase appears twice but is only counted once. The webpage is blocked.

To configure a web content filter in the GUI:

1. Go to Security Profiles > Web Filter and click Create New, or edit an existing profile.

2. In the Static URL Filter section, enable Content Filter.

3. Click Create New.

4. Configure the following settings:

   Pattern Type	Regular Expression
   Pattern	fortinet
   Language	Western
   Action	Block
   Status	Enable

   

5. Click OK and confirm that the entry is added to the table.

   

6. Configure the other settings as needed.

7. Click OK.

To configure a web content filter in the CLI:

1. Create the content (banned word) table:

   config webfilter content
      edit 1
         set name "webfilter"
         config entries
            edit "fortinet"
              set pattern-type regexp
              set status enable
              set lang western
              set score 10
              set action block
            next
         end
      next
   end

2. Apply the content table to the web filter profile:

   config webfilter profile
      edit "webfilter"
         config web
            set bword-threshold 10
            set bword-table 1
         end
         config ftgd-wf
            unset options
         end
      next
   end

To verify the content filter:

1. Go to a website with the word fortinet, such as www.fortinet.com.

   The website is blocked and a replacement page displays: