Debian / Ubuntu Linux: Install SquidGuard Web Filter Plugin For Squid 3.x To Block Unwanted Sites

Posted on in Categories , , last updated June 11, 2013

How do I install and configure SquidGuard – a web filter plugin for Squid to restrict access to domains/URLs based upon access control lists? How do I block porn, gambling, and other web-sites using squid proxy server version 3.x under Debian or Ubuntu Linux server for my school?

squidGuard is flexible and ultra fast filter, redirector and access controller plugin for squid proxy server (it works with both squid version 2.x and 3.x). 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.

Step #1: Install squidguard

Open a terminal and type the following command as root on the server:
# apt-get install squidguard

Step #2: Install Blacklist

The blacklists are the heart of every URL filter. Squidgurd supports both free and commercial distributions of blacklists on the net or create and use your own (or any combination of them). List of free databases:

  1. MESD blacklists (free).
  2. Shalla’s Blacklists (free for non commercial/private use).
  3. Urlblacklist (commercial)

Use wget command to download blacklists from shallalist.de as follows:
# cd /tmp
# wget -c http://www.shallalist.de/Downloads/shallalist.tar.gz
Sample outputs:

--2012-08-22 00:34:16--  http://www.shallalist.de/Downloads/shallalist.tar.gz
Resolving www.shallalist.de... 78.47.242.85
Connecting to www.shallalist.de|78.47.242.85|:80... connected.
HTTP request sent, awaiting response... 206 Partial Content
Length: 9935263 (9.5M), 7448411 (7.1M) remaining [application/x-tar]
Saving to: `shallalist.tar.gz'
 
100%[++++++++++++++============================================>] 99,35,263    475K/s   in 16s     
 
2012-08-22 00:34:33 (459 KB/s) - `shallalist.tar.gz' saved [9935263/9935263]

Untar tar ball, enter:
# tar -zxvf shallalist.tar.gz
Sample outputs:

BL/
BL/porn/
BL/porn/domains
BL/porn/urls
BL/gamble/
BL/gamble/domains
BL/gamble/urls
BL/chat/
BL/chat/domains
BL/chat/urls
BL/automobile/
....
..


BL/radiotv/domains
BL/radiotv/urls
BL/urlshortener/
BL/urlshortener/domains
BL/urlshortener/urls
BL/anonvpn/
BL/anonvpn/urls
BL/anonvpn/domains

In this example, install porn blacklist as follows using the cp command:
# cp -avr BL/porn/ /var/lib/squidguard/db/
Sample outputs:

`BL/porn/' -> `/var/lib/squidguard/db/porn'
`BL/porn/domains' -> `/var/lib/squidguard/db/porn/domains'
`BL/porn/urls' -> `/var/lib/squidguard/db/porn/urls'

Finally, create the database from text files as follows:
# cd /var/lib/squidguard/db/porn
# squidGuard -b -C domains
# squidGuard -b -C urls
Sample outputs:

Processing file and database /var/lib/squidguard/db/porn/domains
    [==================================================] 100 % done
Processing file and database /var/lib/squidguard/db/porn/urls
    [==================================================] 100 % done

Where,

  • -b : Show on progress bar when updating the blacklists.
  • -C fileName : Create new .db files from urls/domain files, which are specified in “fileName”.

Set permissions so that squid can read the files using chown command:
# chown proxy:proxy -R /var/lib/squidguard/db/

Step #3: Configure Squid 3

I’m assuming that Squid 3 is installed and configured properly. Edit /etc/squid3/squid.conf, enter:
# vi /etc/squid3/squid.conf
You need to specify the location of the executable for the URL rewriter using url_rewrite_program as follows:

url_rewrite_program /usr/bin/squidGuard

Save and close the file.

Step #4: Configure SquidGuard

Finally edit /etc/squid/squidGuard.conf, enter:
# vi /etc/squid/squidGuard.conf
Add the following directives:

## Block adult/porn sites for school  ##
dest porn {
        domainlist      porn/domains
        urllist         porn/urls
}

Edit / update acl as follows:

acl {
        default {
                pass  !porn all
                redirect http://192.168.1.11/blocked.html?clientaddr=%a+clientname=%n+clientident=%i+srcclass=%s+targetclass=%t+url=%u
        }
}

Save and close the file. Create a blocked.html on 192.168.1.11 web server:

<html>
	<head>
		<title>URL Blocked</title>
	</head>
	<body>
		<h1>URL Blocked</h1>
		<p>Access to this site / url has been blocked.</p>
		<p>If you think this is an error, please contact the help-desk:</p>
		<p>Call us - 123-456-789 (ext. 333)</p>
		<p>Email us - [email protected]</p>
	</body>
</head>
</html>

Finally, reload the squid 2/3 proxy server:
# /usr/sbin/squid3 -k reconfigure
Verify that both squid and squidguard working properly, run:
# tail -f /var/log/squid3/cache.log
Sample outputs:

2012/08/22 01:23:40| Processing Configuration File: /etc/squid3/squid.conf (depth 0)
2012/08/22 01:23:40| Squid modules loaded: 0
2012/08/22 01:23:40| Adaptation support is off.
2012/08/22 01:23:40| Store logging disabled
2012/08/22 01:23:40| DNS Socket created at [::], FD 8
2012/08/22 01:23:40| DNS Socket created at 0.0.0.0, FD 9
2012/08/22 01:23:40| Adding nameserver 127.0.0.1 from /etc/resolv.conf
2012/08/22 01:23:40| helperOpenServers: Starting 5/5 'squidGuard' processes
2012/08/22 01:23:40| Accepting  HTTP connections at [::]:3128, FD 30.
2012/08/22 01:23:40| HTCP Disabled.
2012/08/22 01:23:40| Loaded Icons.
2012/08/22 01:23:40| Ready to serve requests.

Step #5: Verify the configuration

Type the following command to verify that squidguard is working and blocking the urls:

echo "http://DOMAIN-NAME-HERE / - - GET" | squidGuard -d 
echo "http://sex.com / - - GET" | squidGuard -d

Sample outputs:

2012-08-22 01:26:05 [3365] New setting: dbhome: /var/lib/squidguard/db
2012-08-22 01:26:05 [3365] New setting: logdir: /var/log/squid3
2012-08-22 01:26:05 [3365] destblock good missing active content, set inactive
2012-08-22 01:26:05 [3365] destblock local missing active content, set inactive
2012-08-22 01:26:05 [3365] init domainlist /var/lib/squidguard/db/porn/domains
2012-08-22 01:26:05 [3365] loading dbfile /var/lib/squidguard/db/porn/domains.db
2012-08-22 01:26:05 [3365] init urllist /var/lib/squidguard/db/porn/urls
2012-08-22 01:26:05 [3365] loading dbfile /var/lib/squidguard/db/porn/urls.db
2012-08-22 01:26:05 [3365] squidGuard 1.4 started (1345578965.473)
2012-08-22 01:26:05 [3365] Info: recalculating alarm in 23635 seconds
2012-08-22 01:26:05 [3365] squidGuard ready for requests (1345578965.476)
2012-08-22 01:26:05 [3365] source not found
2012-08-22 01:26:05 [3365] no ACL matching source, using default
http://192.168.1.11/blocked.html?clientaddr=+clientname=+clientident=+srcclass=default+targetclass=porn+url=http://sex.com /- - -
2012-08-22 01:26:05 [3365] squidGuard stopped (1345578965.477)

Or you can see the following in browser:

This URL Has Been Blocked - Opera Browser - SquidGuard with Squid 3 Proxy Server
Fig.01: SquidGuard in action

How do I block other categories?

Update /etc/squid/squidGuard.conf as follows. Define your categories. Just like you did above for porn:

dest gamble {
        domainlist      gamble/domains
        urllist         gamble/urls
}
dest alcohol {
        domainlist      alcohol/domains
        urllist         alcohol/urls
}

Update acl entry as follows:

acl {
        default {
                pass  !porn !gamble !alcohol all
                redirect http://192.168.1.11/blocked.html?clientaddr=%a+clientname=%n+clientident=%i+srcclass=%s+targetclass=%t+url=%u
        }
}

You also need to install database in /var/lib/squidguard/db/ directory:
# cd /tmp
# cp -avr BL/alcohol/ /var/lib/squidguard/db/
# cp -avr BL/gamble/ /var/lib/squidguard/db/
To initializing the blacklists, run:
# squidGuard -C all
Or just initializing newly created categories:
# squidGuard -C /var/lib/squidguard/db/alcohol/domains
squidGuard -C /var/lib/squidguard/db/alcohol/urls
Finally, set permissions:
# chown proxy:proxy -R /var/lib/squidguard/db/
Reload the squid 3:
# /usr/sbin/squid3 -k reconfigure

Do not allow URL filter bypass by the IP addresses

To make sure that users don’t bypass the URL filter by simply using the IP addresses instead of the FQDNs, edit acl entry as follows with !in-addr directive:

acl {
        default {
                pass  !porn !gamble !alcohol !in-addr all
                redirect        http://192.168.1.11/blocked.html?clientaddr=%a+clientname=%n+clientident=%i+srcclass=%s+targetclass=%t+url=%u
        }
}

Reload the squid as follows:
# /usr/sbin/squid3 -k reconfigure

References:
  • man pages – squid(1),squidGuard(1)
  • For more information see squidguard website.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

Share this on (or read 33 comments/add one below):

33 comment

  5. hi,
    i was just confused, i did everything as show here, but the main problem is that all sites are getting blocked?
    i m not sure, maybe i lacked somewhere in the configuration?
    need some help pls…Thanks

    Reply Report comment

  8. Lovely tutorial but my squid will not start if I add “url_rewrite_program /usr/bin/squidGuard” to my squid.conf

    If I do a test with “echo “http://sex.com / – – GET” | squidGuard -d” it works perfectly…

    What is wrong?

    Reply Report comment

  9. I do not understand the line:

    Save and close the file. Create a blocked.html on 192.168.1.11 web server:

    what web server? I made the blocked.html file but where do I put it?

    Reply Report comment

  11. Hello,

    I’ve put together a little script that will update that blacklists. Basically it will download, extract, move the files into place, rebuild the squidGuard databases, and reload the squidGuard processes. Will also send email notifying of success or failure.

    With minor modifications it should work on any system. Tested on Ubuntu 10.04 with distro squid3, and squidGuard 1.6 compiled from squidguard.org.

    Feel free to download at hopefully it will be of use to someone.

    Reply Report comment

  12. Dear Tutor,

    Please help us in blocking facebook with https://facebook.com. I have tried it using Squid on CentOS and DansGuardian for url filtering. But all in vain because users are successful in wasting their time by using fb all day long.

    Please provide UNIX based perfect and industry standard solution to block specifically fb with HTTPS.

    Best Regards,
    SAMEE ULLAH
    Virtual University of Pakistan

    Reply Report comment

  13. Hi,

    I tried to follow through with the tutorial, but the thing is, I’m new and a novice, so I will just describe my situation and you guys should help me through it pls.

    I have a simple network with about 20 users, A Cisco 1940 Series router with IOS 15.01, which is connected to the ISP modem on port g0/1.

    The router’s g0/0 interface is connected to a switch where all the hosts are connected. the Router’s g0/0 interface is 10.10.10.1, cos I’m using a network 10.10.10.0/24.

    I also have a Linux Server with Ubuntu 12.04LTS installed which will act my my Transparent Proxy server to block all unwanted websites (facebook, politics, porn, https) and manage bandwidth, I have installed Squid on the Linux Server. The Linux server IP is 10.10.10.3

    Can anyone please help me with the configuration (on squid, linux and router) required to achieve this?

    Helps.

    Reply Report comment

  15. Having error i this part sir. What seems to be the error? I already chown to proxy:proxy
    Finally, create the database from text files as follows:
    # cd /var/lib/squidguard/db/porn
    # squidGuard -b -C domains
    # squidGuard -b -C urls

    Reply Report comment

  16. Having error i this part sir. What seems to be the error? I already chown to proxy:proxy.

    Finally, create the database from text files as follows:
    # cd /var/lib/squidguard/db/porn
    # squidGuard -b -C domains
    # squidGuard -b -C urls

    Nothing happens when I typed these commands.

    Reply Report comment

  21. The echo command works fine, howerver when I try through a web browser it fails

    Through echo
    2015-04-22 15:24:50 [3339] INFO: squidGuard ready for requests (1429712690.990)
    2015-04-22 15:24:50 [3339] source not found
    2015-04-22 15:24:50 [3339] no ACL matching source, using default
    http//10.0.0.2/blocked.html?clientaddr=-+clientname=+clientident=+srcclass=default+targetclass=ads+url=http://addispenser.com/ -/- – GET
    2015-04-22 15:24:50 [3339] INFO: squidGuard stopped (1429712690.990)

    Through browser (line from /var/log/squid3/cache.log)

    2015/04/22 15:25:17| ERROR: URL-rewrite produces invalid request: GET http//10.0.0.2/blocked.html?clientaddr=10.0.0.100+clientname=+clientident=+srcclass=default+targetclass=ads+url=http://addispenser.com/ HTTP1.1

    Reply Report comment

  23. hey ,
    After copy porn folder to “/var/lib/squidguard/db/”
    and “cd porn/”
    then “squidguard -b -C domains”
    when I add this it gives an error,says that “squidguard: command not found”.How to correct that?Give some help.

    Reply Report comment

  26. Hello,I was stuck on step #2 at
    # cd /var/lib/squidguard/db/porn
    # squidGuard -b -C domains
    # squidGuard -b -C urls

    i go to the directory with the first command, i run either the first or the second command and after pressing enter, the following message comes out:
    “BDB1565 DB->put: method not permitted before handle’s open method”
    if i continue with the following steps,squidguard goes to emergency mode..So,any help please?

    Reply Report comment

  27. Hello,
    I have an issue while i try to compile the backlist with
    # sudo squidGuard -C all
    Nothing happens…
    I’ve tested it with just 2 or 3 domians and it works fine but with Shalla’s Blacklist it does nothing.

    Reply Report comment

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