How To Block Porn Pictures And Images With SafeSquid Proxy Server

Administrators can use various methods to block access to websites that are pornographic in nature, like URL Filter, URL Blacklist, Keyword Filter, etc. But many porn sites allow users to register their email IDs on their website and deliver the latest images and pictures to their personal emails. So if a user is allowed access to his personal mail, he can enjoy himself without having to access any porn site. Such images are also regularly displayed as ads and banners on other web pages, that might not be pornographic in nature.

Pornographic Image Filter can analyze an image in real-time, and identify the ones that are pornographic in nature. It analyzes the graphical content like skin tone, contour, etc. to identify a pornographic image. It is a commercially distributed add-on plug-in and can be used with SafeSquid to block pornographic images. Although it is about 85%-90% accurate, it acts as a good deterrent.

Follow the procedure below to install Pornographic Image Filter and use it with SafeSquid:

Download the trial Pornographic Image Filter Add-on Module from the SafeSquid Downloads Page and copy it to a directory on the SafeSquid Server, e.g. in /usr/local/src.

The add-on module is about 11MB in size and although it is an expired trial version, you can install the files. Once the installation is complete, you can request for fresh trial binary files by sending a request email to information@safesquid.net. Just replace the files that you receive in the installation directory.

Change directory to /usr/local/src

cd /usr/local/src

Untar the file imagefilter.trial.20080730.tar.gz

tar -xzvf imagefilter.trial.20080730.tar.gz

Change directory to imagefilter.trial.20080730.tar.gz

cd imagefilter.trial.20080730

The directory contains the following files:

drwxr-xr-x 3 root root 4096 Sep 4 17:26 imgfilter
-rwxr-xr-x 1 root root 20168 Sep 4 17:28 imgfilter.so
-rw-r--r-- 1 root root 2087 Sep 4 17:30 imgfilter.xml
-rw-r--r-- 1 root root 872160 Sep 4 17:28 libimgfilter.so

Create 'imgfilter' directory in /opt/safesquid/modules/

mkdir /opt/safesquid/modules/imgfilter

Copy the files to /opt/safesquid/modules/imgfilter

cp imgfilter.so /opt/safesquid/modules/imgfilter
cp imgfilter.xml /opt/safesquid/modules/imgfilter
cp libimgfilter.so /opt/safesquid/modules/imgfilter
cp -r imgfilter /opt/safesquid/modules/imgfilter

Create symbolic links for loading image filter module

cd /opt/safesquid/modules
ln -fs /opt/safesquid/modules/imgfilter/imgfilter.so imgfilter.so
ln -fs /opt/safesquid/modules/imgfilter/imgfilter.xml imgfilter.xml
ln -fs /opt/safesquid/modules/imgfilter/libimgfilter.so /lib/libimgfilter.so

Restart SafeSquid

/etc/init.d/safesquid restart

Now when you access the SafeSquid Interface, you should find a new section 'Image filter' under 'Config'.

When you request for a fresh trial copy, you will receive the file imgfilter.so.
Just copy this file to /opt/safesquid/modules/imgfilter
This will renew your trial period.

Now, to configure the Image filter section in the SafeSquid Interface, go to Config => Image filter.
You will see a screen similar to this:

Click on Add under the Image filters subsection to add a new filter rule.

Specify the Profiles to which you want to apply this rule.
Leave it blank to apply to all.

You can configure the sensitivity of the filter by specifying the Threshold option.
Image filter allocates a score to all the images that it analyzes. -10.0 is unlikely to be porn whereas 0.0 is very likely.
To start with, keep the Threshold value 0.0. You can then fine tune the filter by altering this value.
You can also create multiple rules, with different Threshold limits for different Profiles.

When an image is blocked, it will appear as a blank box. You can also replace a blocked image with a custom image.
For example, if you fill in the Default template value with checkeredgif, which is a custom image that comes with SafeSquid, the image will be replace with a checkered box, as shown below:

Also see:

• Deploying A Content Filtering Proxy Server To Distribute Controlled Internet Access With SafeSquid
• Set Up Gateway Level Virus Security With ClamAV And SafeSquid Proxy
• How To Set Up Internet Access Control And Internet Filtering With SafeSquid Proxy Server
• How To Control Access To Unwanted Websites Using URL Blacklist With SafeSquid Proxy Server
• How To Configure Granular Bandwidth Management Rules In SafeSquid Proxy Server
• How To Control Download Of Files And Mime Types In SafeSquid Proxy Server
• How To Block Ads And Banners In SafeSquid Proxy Server
• How To Block Cookies From Unwanted Websites With SafeSquid Proxy Server
• Enhance Security By Removing ActiveX Control Codes From Web Pages With SafeSquid Proxy Server
• How To Block WebPages Based On Keywords Or Phrases With SafeSquid Proxy Server
• How To Control Or Block Instant Messengers With SafeSquid Proxy Server
• How To Enforce Google SafeSearch With SafeSquid Proxy Server

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