Symantec Security 5600 Series, Security 5400 Series,Clientless VPN 4400 Series, Руководство администратора

Страница: 297 / 861

296 Controlling traffic at the security gateway
Blocking inappropriate content with content filtering
Content filtering processing order
The security gateway filters email for content in a specific sequence. If a content filtering scanning
process in the sequence is not enabled, the security gateway moves to the next scanning process that is
enabled.
The content filters are applied in the following order:
■
Filtering by URL
See
“Filtering by a specific URL” on page 297.
■
URL filtering using pattern matching
See
“Filtering by URL pattern matching” on page 299.
■
Filtering by MIME type
See
“Filtering by MIME type” on page 302.
■
Filtering by file extension
See
“Filtering by file extension” on page 304.
■
Filtering by content categories
See
“Creating a content profile” on page 311.
■
Filtering by DDR
See
“About Dynamic Document Review (DDR)” on page 309.
Note:
If HTTP traffic is denied for any reason, the security gateway stops processing for content
filtering.
Filtering content by allowing or denying access to defined settings
You can filter content at the proxy level based on the following parameters:
After you specify the URLs, URL patterns, MIME types, and file extensions to which users are allowed
or denied access, you can apply these settings selectively in rules. When traffic defined by a rule passes
through the security gateway, the settings are processed in order of precedence, as described in
“Content filtering processing order” on page 296.
For example, you can create a list of URLs that should be allowed and a second list of file extensions
that should be allowed. When you create a rule that applies these restrictions to HTTP traffic, the
security gateway first applies the list of URLs to the traffic to see if it is allowed. It then applies the list
of file extensions. Only traffic that is defined in both lists is allowed.
Complete these procedures to set up filtering:
■
Filtering by a specific URL
■
Filtering by URL pattern matching
■
Filtering by MIME type
■
Filtering by file extension
Specific URL You can allow or deny user access to specified URLs.
URL pattern
matching You can supply pattern matching parameters to block common patterns that indicate
certain types of content.
MIME type You can allow or deny user access to selected MIME types.
File extension You can allow or deny user access to specified file extensions.