D-Link DFL-210 - NetDefend - Security Appliance, User Manual

Page: 245 / 469

1. Go to Objects > ALG
2. In the table, click on the recently created HTTP ALG to view its properties
3. Click the HTTP URL tab
4. Now click Add and select HTTP ALG URL from the menu
5. Select Whitelist as the Action
6. In the URL textbox, enter www.D-Link.com/*.exe
7. Click OK
Simply continue adding specific blacklists and whitelists until the filter satisfies the needs.
6.3.4. Dynamic Web Content Filtering
6.3.4.1. Overview
As part of the HTTP ALG, 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.
WCF Databases
NetDefendOS WCF allows web page blocking to be automated so 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, adult-oriented and so on.
The WCF URL databases are updated almost hourly with new, categorized URLs while at the same
time older, invalid URLs are dropped. The scope of the URLs in the databases is global, covering
websites in many different languages and hosted on servers located in many different countries.
Dynamic Web Content Filtering Availability on D-Link Models
Dynamic Content Filtering is available on the D-Link DFL-260 and DFL-860 only.
WCF Processing Flow
When a user requests access to a web site, NetDefendOS sends a query to the WCF databases in
order 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 6.6. Dynamic Content Filtering Flow
6.3.4. Dynamic Web Content Filtering Chapter 6. Security Mechanisms
245