If someone wants to access specific contents, they usually will find a loophole to do so. That does not mean that parents should not restrict access to those sites as best as they can. This article takes a look at some of the options provided. Now, all of those solutions are solutions for a single computer system, or a small network of computers. They do not prevent a child from visiting a friend’s house to view all the contents that are blocked at home. And they do not block contents that are already on the PC or transferred to the PC from mobile devices, hard drives or DVDs.

DNS Providers With Filtering Options

The domain name system (DNS) is used to “translate” web addresses into IP addresses. This is usually done by the Internet Service Provider, with the option to switch to another provider. Users who switch providers usually do that for one of the following reasons:

• Censorship on part of the ISP
• Faster DNS lookups
• Filtering options and other additional features

One of the DNS providers that offers filtering is Open DNS. There are others that offer similar services, just search on Bing or another search engine for them. Users who create a free account at the Open DNS website can configure the filtering options in detail.

web content filtering

Here it is possible to select one of the preconfigured filtering levels (e.g. High for blocking 26 different site categories from adult themed over tasteless to P2P file sharing and drugs). There is also a custom option that gives the user the option to define the categories that should be filtered out automatically.

Filtering means that sites that fall into those categories will not be displayed to the computer user. Filters are only as good as their detection algorithms, and it can happen that sites slip past them. Parents who find out about those sites can add them to the filtering list manually to block them in the future.

block pornographic websites

A user visiting one of those websites will see a message like the one shown in the screenshot above. Open DNS is offering a special service that they call FamilyShield. It is basically a custom filtering configuration that blocks adult sites, anonymizers and proxies, phishing and malware sites.

Verdict: Efficient filtering options that work on all devices configured to use the new DNS provider, but difficulty to configure for non-tech-savvy computer users.

Google Safe Search Filtering

Google is the most popular search engine in the world. Google, and other search engines like Bing, offer so called safe search filters to filter out search results that are deemed inappropriate. Google by default applies moderate filtering to search results. Moderate means that the search engine filters out explicit images. This can be changed to strict filtering to filter text and images from the search results, or no filtering for users who prefer to see all results regardless of their nature.

safe search settings in Google Search Settings

Google recently has added an option to lock the safe search filtering settings. Once done an image is shown on all Google pages indicating that safe search filtering is active.

Verdict: The settings are relatively effective, but very easy to bypass. All it takes is to switch to another search engine, Internet browser, or clear the cookies of the standard browser to reset the safe search filtering settings. Good additional option but to weak as the standalone filtering option.

Browser add-ons

Browser add-ons are another option to block pornographic websites. Firefox users can for instance install Foxfilter, a filtering add-on that automatically scans every page load and determines whether the page needs to be blocked or not. Blocked pages are indicated to the user.

content filter

The settings offer options to add websites to a whitelist, in case they get blocked but should not be. Other add-ons and plugins that fall into this category are Censure Block or Christian Anti-Porn for Firefox, Kid Safe for Chrome (which only displays a warning but does not block) or Simple Profanity Filter.

Like settings for specific search engines, browser add-ons are limited to their environment. If a user switches to another browser, then nothing can be done about it.

Parent Control, Filtering Applications

Most parental control applications come at a cost. There are a few free solutions available, like Untangle which basically is a security software with a web filtering component. Still, most tools are commercial in nature and therefor not included in this review. Several commercial security suites also come with parental controls to block specific types of websites.

Verdict: Applications often block contents on a system wide level, as long as they are running on the user’s account as well. There are still options to circumvent applications, for instance by booting from a Linux Live CD or connecting another system to the router directly.

Misc blocking options

Block Porn with Proxy Auto Configuration Files [link], very technical in nature, and limited to the browser the proxy is configured in.

How To Block Porn Pictures And Images With SafeSquid Proxy Server [link], aimed at system administrators and not end users.

Verdict

Blocking porn with DNS filtering appears to the most effective option for most environments. It has to be noted that this is effective, but not fool proof either. Children with enough determination and time will eventually find a way to bypass the restrictions, if they are determined to do so.

Let us know in the comments if you know of another free option to block porn and other contents on the internet.

The web filter is fully customizable to block only the selected contents in the network the DNS servers are used. Those filtering customizations are on the other hand only available for free or paid OpenDNS account owners and not for users who have simply switched their DNS servers to the provider.

OpenDNS FamilyShield has been designed for families who want a ready to run solution. The DNS servers come with family friendly filtering activated so that account creation and configuration is not necessary.

Filters to block adult contents, proxies and anonymizers are automatically active after changing the DNS servers to the FamilyShield IPs.

DNS servers have an advantage over parental control software as they can be configured on a computer system or router. All devices that use the router to connect to the Internet are benefiting from the web filtering and additional security. Parental control software on the other hand can only be installed on supported computer systems and not devices such as Microsoft’s Xbox 360, Sony’s Playstation 3, Nintendo’s Wii or 3Ds as they are usually operating system specific.

The DNS server IPs that need to be used are 208.67.222.123 and 208.67.220.123. These need to be entered into the router configuration or computer configuration, depending largely on the network setup and situation.

opendns familyshield

The OpenDNS Knowledge Base contains information on how to setup the DNS servers on various operating systems and devices.

Advanced users might prefer the manual approach by creating an account to block only specific web contents. Families on the other hand can use the DNS servers to install a solid web filtering solution without the hassles of configuration.

The German Federal Criminal Office has the authority to add new websites and domains to the list. A website can for instance be added instantly if it is hosted outside of the European Union. A committee has been designated to perform spot checks on the list every three months.

The law itself was pushed mainly as a law to fight child pornography on the Internet. It was always denied that it would be used to censor websites for different reasons although some politicians have already mentioned that they would like to include violent video games or hate sites in the list as well.

Internet providers have the sole responsibility to provide the infrastructure and maintain the web censorship filters. This includes organizations like Universities but also some businesses with more than 10000 employees. The technique employed to filter websites that are on the web censorship list is simply blocking the domain name. Users who enter the IP can visit the site normally. (via Heise (German))