Web Gateway 7.1.5 Product Guide - McAfee

HTML filtering
Web filtering
HTML filtering 6
The appliance can filter HTML pages and remove embedded objects from them. This section explains
HTML filtering and describes the rules, lists and module settings involved in the filtering process.
Rules for HTML filtering typically say whether er objects embedded in HTML pages should be removed
or kept. They evaluate object types and use also filter lists. They call an opener module to make
embedded objects accessible for filtering.
The types of objects HTML filtering can remove include the following:
• Java applets — Are embedded in HTML pages (unlike the stand-alone Java applications) and run,
once their certificates are accepted, with all privileges of the current user
• ActiveX controls — Run with all privileges of the user
• Scripts — Include JavaScript, JScript, and Visual Basic Script
• Media types — Include text, audio, image, streaming, and other media types
Rules for HTML filtering
To enable HTML filtering on the appliance, a rule set containing appropriate rules must be implemented.
This section describes a sample rule set from the rule set library.
After the initial setup, an HTML filtering rule set is not implemented on the appliance. You can import
the HTML Filtering rule set from the library and modify it according to your requirements or create a
rule set of your own.
For more information, see Import a rule set and HTML Filtering (rule set).
HTML Filtering (rule set)
This section describes the rules of a library rule set for HTML Filtering.
For general information on understanding and handling rules, see Rules and rule sets.
Library rule set — HTML Filtering
Criteria — Always
Cycles — Requests (and IM), responses, embedded objects
The rule set contains a rule and the following two nested rule sets:
• Enable HTML Filtering
• HTML Filtering
The following rule is contained in the rule set in addition to the nested rules sets:
Remove Content-Encoding header
Always –> Continue — Header.RemoveAll (“Accept-Encoding”)
The rule uses an event to remove the content encoding header from a request.
This header is not needed because filtering is only applied to the content, which is eventually sent
in not encoded format to the user who requested it. The name of the header is specified by the
event parameter.
Processing continues with the next rule set.
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