ZyXEL Communications ZyWall 110 User Manual page 713

Figure 500 Content Filter Lookup Procedure
A computer behind the Zyxel Device tries to access a web site.
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The Zyxel Device looks up the web site in its cache. If an attempt to access the web site was made in the
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past, a record of that web site's category will be in the Zyxel Device's cache. The Zyxel Device blocks,
blocks and logs or just logs the request based on your configuration.
Use the Content Filter Cache screen to configure how long a web site address remains in the cache as
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well as view those web site addresses. All of the web site address records are also cleared from the local
cache when the Zyxel Device restarts.
If the Zyxel Device has no record of the web site, it queries the external content filter database and
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simultaneously sends the request to the web server.
The external content filter server sends the category information back to the Zyxel Device, which then
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blocks and/or logs access to the web site based on the settings in the content filter profile. The web
site's address and category are then stored in the Zyxel Device's content filter cache.
Chapter 37 Content Filtering
ZyWALL USG Series User's Guide
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