Static Content Filtering; Stripping Activex And Java Applets - D-Link DFL-260E User Manual

6.3.3. Static Content Filtering

Example 6.13. Stripping ActiveX and Java applets
This example shows how to configure a HTTP Application Layer Gateway to strip ActiveX and Java applets. The
example will use the content_filtering ALG object and assumes one of the previous examples has been done.
Command-Line Interface
gw-world:/> set ALG ALG_HTTP content_filtering
Web Interface
1. Go to Objects > ALG
2. In the table, click on our HTTP ALG object, content_filtering
3. Check the Strip ActiveX objects (including flash) control
4. Check the Strip Java applets control
5. Click OK
6.3.3. Static Content Filtering
Through the HTTP ALG, NetDefendOS can block or permit certain web pages based on configured
lists of URLs which are called blacklists and whitelists. This type of filtering is also known as Static
Content Filtering. The main benefit with Static Content Filtering is that it is an excellent tool to
target specific web sites, and make the decision as to whether they should be blocked or allowed.
Static and Dynamic Filter Ordering
Additionally, Static Content Filtering takes place before Dynamic Content Filtering (described
below), which allows the possibility of manually making exceptions from the automatic dynamic
classification process. In a scenario where goods have to be purchased from a particular on-line
store, Dynamic Content Filtering might be set to prevent access to shopping sites by blocking the
"Shopping" category. By entering the on-line store's URL into the HTTP Application Layer
Gateway's whitelist, access to that URL is always allowed, taking precedence over Dynamic
Content Filtering.
Wildcarding
Both the URL blacklist and URL whitelist support wildcard matching of URLs in order to be more
flexible. This wildcard matching is also applicable to the path following the URL hostname which
means that filtering can be controlled to a file and directory level.
Below are some good and bad blacklist example URLs used for blocking:
*.example.com/*
www.example.com/*
Removing such legitimate code could, at best, cause the web site to look distorted, at
worst, cause it to not work in a browser at all. Active Content Handling should
therefore only be used when the consequences are well understood.
RemoveActiveX=Yes RemoveApplets=Yes
Good. This will block all hosts in the example.com domain and all web
pages served by those hosts.
Good. This will block the www.example.com website and all web pages
served by that site.
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Chapter 6. Security Mechanisms