42.7 squidGuard
This section is not intended to explain an extensive configuration of
squidGuard, only to introduce it and give some
advice for using it. For more in-depth configuration issues, refer to the
squidGuard Web site at https://www.squidguard.org.
squidGuard is a free (GPL), flexible, and fast
filter, redirector, and access controller plug-in for
Squid. It lets you define multiple access rules
with different restrictions for different user groups on a
Squid cache. squidGuard uses Squid's standard redirector interface.
squidGuard can do the following:
-
Limit the Web access for some users to a list of accepted or well-known
Web servers or URLs.
-
Block access to some listed or blacklisted Web servers or URLs for some
users.
-
Block access to URLs matching a list of regular expressions or words for
some users.
-
Redirect blocked URLs to an intelligent
CGI-based
information page.
-
Redirect unregistered users to a registration form.
-
Redirect banners to an empty GIF.
-
Use different access rules based on time of day, day of the week,
date, etc.
-
Use different rules for different user groups.
squidGuard and Squid cannot be used to:
-
Edit, filter, or censor text inside documents.
-
Edit, filter, or censor HTML-embedded script languages, such as
JavaScript or VBscript.
Before it can be used, install squidGuard. Provide a minimal configuration
file as /etc/squidguard.conf. Find configuration
examples in https://www.squidguard.org/config/. Experiment
later with more complicated configuration settings.
Next, create a dummy access denied
page
or a more or less complex CGI page to redirect Squid if
the client requests a blacklisted Web site. Using
Apache is strongly recommended.
Now, configure Squid to use squidGuard. Use the
following entry in the /etc/squid/squid.conf file:
redirect_program /usr/bin/squidGuard
Another option called redirect_children
configures the number of redirect
(in this case
squidGuard) processes running on the
machine. squidGuard is fast enough to handle
many requests: on a 500 MHz Pentium with 5,900 domains and 7,880
URLs (totaling 13,780), 100,000 requests can be processed within
10 seconds.
Therefore, it is not recommended to set more than four processes, because the
allocation of these processes would consume an excessive amount of memory
redirect_children 4
Last, have Squid load the new configuration by
running rcsquid reload. Now, test
your settings with a browser.
