Dynamic Web Content Filtering; Dynamic Content Filtering Flow - D-Link NetDefend DFL-210 User Manual

6.3.4. Dynamic Web Content Filtering

6.3.4. Dynamic Web Content Filtering
Overview
NetDefendOS supports Dynamic Web Content Filtering (WCF) of web traffic, which enables an
administrator to permit or block access to web pages based on the content of those web pages. This
functionality is automated and it is not necessary to manually specify which URLs to block or allow.
Instead, D-Link maintains a global infrastructure of databases containing massive numbers of
current web site URL addresses, grouped into a variety of categories such as shopping, news, sport
and adult-oriented on so on. These databases are updated every hour with new, categorized URLs
while at the same time older, invalid URLs are dropped. The database content is global, covering
websites in many different languages and which are hosted in countries around the world.
URL Processing Flow
When a user requests access to a web site, NetDefendOS sends a query to these databases to retrieve
the category of the requested site. The user is then granted or denied access to the site based on the
filtering policy 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 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 6.2. 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 techniques including neural networks and pattern matching. Once
categorized, the URL is distributed to the global databases and NetDefendOS receives the category
for the URL. Dynamic Content Filtering therefore requires a minimum of administration effort.
Dynamic Web Content Filtering Availability on D-Link Models
Dynamic Content Filtering is available on the D-Link DFL-260 and DFL-860 only.
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Chapter 6. Security Mechanisms