ZyXEL Communications 5 Series User Manual

Chapter 17 Content Filtering Screens

ZyWALL 5/35/70 Series User’s Guide

Figure 187   Content Filtering Lookup Procedure

1 A computer behind the ZyWALL tries to access a web site.
2 The ZyWALL looks up the web site in its cache. If an attempt to access the web site was 

made in the past, a record of that web site’s category will be in the ZyWALL’s cache. 
The ZyWALL blocks, blocks and logs or just logs the request based on your 
configuration. 

3 Use the CONTENT FILTER Cache screen to configure how long a web site address 

remains in the cache as well as view those web site addresses (see 

). All of the web site address records are also cleared from the local cache when the 

ZyWALL restarts.

4 If the ZyWALL has no record of the web site, it will query the external content filtering 

database and simultaneously send the request to the web server.

The external content filtering database may change a web site’s category or categorize a 
previously uncategorized web site. 

5 The external content filtering server sends the category information back to the 

ZyWALL, which then blocks and/or logs access to the web site. The web site’s address 
and category are then stored in the ZyWALL’s content filtering cache.

Content filtering policies allow you to have different content filtering settings for different 
users or groups of users. For example, you may want to block most employees from accessing 
finance or stock websites, but allow the finance department to access these. You can set the 
ZyWALL to use external database content filtering and select which web site categories to 
block and/or log. 

• See 

Click SECURITY > CONTENT FILTER to open the General screen. Use this screen to 
enable content filtering and configure general settings. 

"

You must register for external content filtering before you can use it.