D-Link NetDefend DFL-1660, User Manual

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WCF Processing Flow
When a user of a web browser requests access to a web site, NetDefendOS queries the Dynamic
WCF databases in order to retrieve the category of the requested site. Access to the URL can then be
allowed or denied based on the filtering policy that the administrator has put in place for that
category.
If access is denied, a web page will be presented to the user explaining that the requested site has
been blocked. To make the lookup process as fast as possible NetDefendOS maintains a local cache
in memory of recently accessed URLs. Caching can be highly efficient since a given user
community, such as a group of university students, often surfs to a limited range of websites.
Figure 6.8. Dynamic Content Filtering Flow
If the requested web page URL is not present in the databases, then the webpage content at the URL
will automatically be downloaded to D-Link's central data warehouse and automatically analyzed
using a combination of software techniques. Once categorized, the URL is distributed to the global
databases and NetDefendOS receives the category for the URL. Dynamic WCF therefore requires a
minimum of administration effort.
Note: New URL submissions are done anonymously
New, uncategorized URLs sent to the D-Link network are treated as anonymous
submissions and no record of the source of new submissions is kept.
Categorizing Pages and Not Sites
NetDefendOS dynamic filtering categorizes web pages and not sites. In other words, a web site may
contain particular pages that should be blocked without blocking the entire site. NetDefendOS
provides blocking down to the page level so that users may still access parts of websites that are not
6.3.4. Dynamic Web Content Filtering Chapter 6. Security Mechanisms
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