Ways To Block Pornographic Websites

Martin Brinkmann
Sep 27, 2010
Updated • Dec 27, 2012

The free nature of the Internet makes it more or less uncontrollable, which can be a problem for parents, teachers, businesses and the government. Parents for instance usually want to make sure that their children do not visit unsuitable websites. The problem that they encounter is that it is virtually impossible to block all pornographic, adult, violent or other unsuitable types of websites. Why? Because there are virtually endless possibilities to access those contents, and no fool proof options to block them all.

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
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
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
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
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.


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.


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  1. Cole said on October 19, 2010 at 7:37 pm

    Excellent info – I appreciate it & your readers’ comments as well. Ty – Thanks so much for this suggestion. I actually took the time to check out Pandora’s hope & have it on order for my family. We are anxious to get it installed and running. I know my wife & I already feel much better about the future of our kids & their internet interaction. Thanks again for sharing!

  2. Ty said on October 13, 2010 at 5:31 am

    Interesting article! Thanks for keeping us informed with all the latest. If your readers are looking for an easy solution to help with internet safety check this out – I recently found a new device that is excellent & wanted to share with you & your readers. Pandora’s Hope is a solution to easily protect homes or businesses from those things online that you  don’t want to be exposed to or tempted by.The Pandora’s Hope router connects directly into your modem, making it easy to use and compatible with any cable or DSL Internet connection. This Internet filtering router gives you better control on what is seen on any device using your Internet connection (wireless or via cable). Definitely worth checking out – works great EXTREMELY easy set up!

  3. Bill said on October 5, 2010 at 12:13 am

    I’ve never tried DNS filtering. I may have to try that now. Thanks!

  4. adelpro said on September 28, 2010 at 5:26 pm

    thinks for the comments Will

    but what do you mean by forcing devices… and port 53…. can you explain as how to do that
    it likes interesting

  5. Will said on September 28, 2010 at 9:01 am

    I prefer K9 for filtering (nicer to temp allow when needed) but use OpenDNS via router to force all devices to use it for DNS via Firewall setting. Any traffic on port 53 is automatically routed to OpenDNS no matter what the user sets as their DNS. :)

  6. JMason said on September 27, 2010 at 10:28 pm

    I also use OpenDNS and K9 filter combination for my home desktop and laptops. I would say they will effectively block 95+ % of garbage out there. Very easy to set up too, both have great help documentation.

  7. Laura Oppenheimer said on September 27, 2010 at 10:24 pm

    Hi Ahmed,

    The best thing to do would be to drop our support team a note here: http://www.opendns.com/support/contact/

    They can take a look at what’s happening :)


  8. Ahmad said on September 27, 2010 at 9:46 pm

    Thanks for nice article Martin.
    I have one question for Laura. I have ZTE ZXDSL 831 Router, I am unable to change my router DNS, if I change it and restart it, it comes back to my ISP DNS. I need some sort of help from you. Thanks in advance.


  9. Laura Oppenheimer said on September 27, 2010 at 8:08 pm

    Hi Adelpro,

    That isn’t something we have in the works right now, but we’re always interested in new features and enhancements. We love seeing suggestions from our users in IdeaBank: http://ideabank.opendns.com/. Many recent enhancements have come directly from there!


  10. adelpro said on September 27, 2010 at 8:06 pm

    just wana ask if you are planing a firefox add for the management of whit black list just inside firefox directly


  11. adelpro said on September 27, 2010 at 8:02 pm

    thiks for this article
    im using OpenDNS solution its very good not just for porn filtering but as anti-maleware and virus…. anti-phishing solution

    but its very simple to bypass
    but if this solution is assossiated with K9 a filtering software (free license for 3 PCs) its perfect

    the K9 ist hard to bypass for normal user

    hoop that that help and thinks for all the GHacks users

  12. Laura Oppenheimer said on September 27, 2010 at 7:37 pm

    One of the reasons Web content filtering at the DNS level is also a good idea is because it doesn’t slow down your computer! Many software-based solutions can be a little unwieldy. Plus, using OpenDNS protects you from phishing and malware sites, as well :)

    If you or your readers ever have any questions about OpenDNS, please get in touch!


  13. Transcontinental said on September 27, 2010 at 4:49 pm

    Thanks for this post Martin.
    I’m concerned when kids may happen to be around (I usually close the computer, but sometimes hard to though); DNS filtering is the easiest, that is if the kids aren’t aware that changing the resolvers is easy. I wonder if there is any password-based application that forbids modifying the DNServers (on the Registry level I presume).

    1. Martin said on September 27, 2010 at 5:14 pm

      You can do that in the Group Policy Editor under User Configuration > Network > Network Connections > Prohibit TCP / IP advanced configuration. If you enable that the Properties dialog becomes inaccessible.

      1. Transcontinental said on September 27, 2010 at 5:34 pm

        I wasn’t aware of that possibility, thanks for the hint, Martin.

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