Chapter 32 Content Filtering

External Content Filter Server Lookup Procedure

The content filter lookup process is described below.

Figure 317 Content Filter Lookup Procedure

1A computer behind the ZyWALL tries to access a web site.

2The 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.

3Use 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 Section 9.16 on page 200). All of the web site address records are also cleared from the local cache when the ZyWALL restarts.

4If the ZyWALL has no record of the web site, it queries the external content filter database and simultaneously sends the request to the web server.

5The external content filter server sends the category information back to the ZyWALL, which then 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 ZyWALL’s content filter cache.

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ZyWALL USG 50 User’s Guide