Enabling Audit Mode - D-Link NetDefend DFL-210 User Manual

6.3.4. Dynamic Web Content Filtering
easier to evaluate if the goals of site blocking are being met.
Example 6.16. Enabling Audit Mode
This example is based on the same scenario as the previous example, but now with audit mode enabled.
Command-Line Interface
First, create an HTTP Application Layer Gateway (ALG) Object:
gw-world:/> add ALG ALG_HTTP content_filtering
Web Interface
First, create an HTTP Application Layer Gateway (ALG) Object:
1. Go to Objects > ALG > Add > HTTP ALG
2. Specify a suitable name for the ALG, for example content_filtering
3. Click the Web Content Filtering tab
4. Select Audit in the Mode list
5. In the Blocked Categories list, select Search Sites and click the >> button
6. Click OK
The steps to then create a service object using the new HTTP ALG and modifying the NAT rule to use the new
service, are described in the previous example.
Allowing Override
On some occasions, Active Content Filtering may prevent users carrying out legitimate tasks.
Consider a stock broker dealing with on-line gaming companies. In his daily work, he might need to
browse gambling web sites to conduct company assessments. If the corporate policy blocks
gambling web-sites, he will not be able to do his job.
For this reason, NetDefendOS supports a feature called Allow Override. With this feature enabled,
the content filtering component will present a warning to the user that he is about to enter a web site
that is restricted according to the corporate policy, and that his visit to the web site will be logged.
This page is known as the restricted site notice. The user is then free to continue to the URL, or
abort the request to prevent being logged.
By enabling this functionality, only users that have a valid reason to visit inappropriate sites will
normally do so. Other will avoid those sites due to the obvious risk of exposing their surfing habits.
Reclassification of Blocked Sites
As the process of classifying unknown web sites is automated, there is always a small risk that some
sites are given an incorrect classification. NetDefendOS provides a mechanism for allowing users to
WebContentFilteringMode=Audit
FilteringCategories=SEARCH_SITES
Caution: Overiding the restriction of a site
If a user overrides the restricted site notice page, they are allowed to surf to all pages
without any new restricted site message appearing again. The user is however still
being logged. When the user has become inactive for 5 minutes, the restricted site
page will reappear if they then try to access a restricted site.
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Chapter 6. Security Mechanisms