Sidewinder G2 6.1.1 Administration Guide - Glossary of Technical ...

Configuring MIME filtering
rules
Creating Mail Application Defenses
When you click New or Modify beneath the MIME/Anti-Virus Filter
Rules area, the MIME Rule Edit window appears. This window allows
you to add or modify a MIME filtering rule.
Important: Rules that are configured with an Allow or Deny action will allow or deny
messages based on the rule criteria that is defined within the rule. Allow and deny rules do
not perform virus scanning. To perform virus scanning for messages that match a rule
before it is allowed, you must specify Virus Scan in the rule’s Action field.
By default, a single allow rule is contained in the filter rule table. If
you choose to leave the default allow rule as the last rule in your table
(that is, all mail that isn’t explicitly denied will be allowed), you will
need to configure the appropriate virus scan and/or deny rules and
place them in front of the default allow rule.
If you configure the default rule action to deny (that is, all mail that is
not explicitly allowed will be denied) you will need to configure the
appropriate virus scan and/or allow rules and place them in front of
the default deny rule. In this scenario, if you want to allow multi-part
mixed MIME elements within a mail message (which is fairly
common) you will need to create an allow rule with Multipart selected
in the Type field and Mixed selected in the Subtype field. If you do not
create this type of allow rule when using a default deny rule, any mail
message that contains multiple MIME types will be denied.
To configure MIME/Virus Filter rules, follow the steps below.
Note: Rules that specify both a MIME type/subtype and file extensions will allow or deny
any traffic that matches either the MIME Type or a File Extension type. That is, the traffic
does not need to match both criteria to match the rule.
1. In the MIME Type drop-down list, select the MIME type for which you
want to filter. If you select the asterisk (*) option, the filter rule will ignore
this field when determining a match.
2. In the MIME Subtype drop-down list, select a subtype for the MIME type
that you selected in the previous step (the available options will vary
depending on the MIME type you selected in the previous step). If you
select the asterisk (*) option, the filter rule will ignore this field when
determining a match.
Configuring Application Defenses 6-29