Web content filter

The content filter analyzes all web traffic and blocks selected websites or sites containing viruses. Forbidden sites are selected from a list of categories, which in turn must be downloaded from external sources and stored on the system.

The system allows to create an infinite number of profiles. A profile is composed by three parts:

  • Who: the client associated with the profile. Can be a user, a group of users, a host, a group of hosts, a zone or an interface role (like green, blue, etc).
  • What: which sites can be browsed by the profiled client. It’s a filter created inside the Filters section.
  • When: the filter can always be enabled or valid only during certain period of times. Time frames can be created inside the Times section.

This is the recommended order for content filter configuration:

  1. Select a list of categories from Blacklists page and start the download
  2. Create one or more time conditions (optional)
  3. Create custom categories (optional)
  4. Create a new filter or modify the default one
  5. Create a new profile associated to a user or host, then select a filter and a time frame (if enabled)

If no profile matches, the system provides a default profile that is applied to all clients.

Filters

A filter can:

  • block access to categories of sites
  • block access to sites accessed using IP address (recommended)
  • filter URLs with regular expressions
  • block files with specific extensions
  • enable global blacklist and whitelist

A filter can operate in two different modes:

  • Allow all: allow access to all sites, except those explicitly blocked
  • Block all: blocks access to all sites, except those explicitly permitted

Note

The category list will be displayed only after the download of list selected from :guilabel`Blacklist` page.

Blocking Google Translate

Online translation services, like Google Translate, can be used to bypass the content filter because pages visited trough the translator always refer to a Google’s domain despite having content from external servers.

It’s possible to block all requests to Google translate, creating a blocked URL inside the General page. The content of the blocked URL must be: translate.google.

Antivirus

Web browsing can be checked for malicious content, but only for clear text HTTP protocol. If the proxy is configured in SSL transparent mode (SSL Proxy), content downloaded via HTTPS will not be scanned.

Troubleshooting

If a bad page is not blocked, please verify:

  • the client is surfing using the proxy
  • the client doesn’t have a configured bypass inside Hosts without proxy section
  • the client is not browsing a site with a configured bypass inside Sites without proxy section
  • the client is really associated with a profile not allowed to visit the page
  • the client is surfing within a time frame when the filter is permissive