Porn Filters Compared: OpenDNS, Neustar, CleanBrowsing, Norton, Yandex and AdGuard

On a , I provided some details on a disappointing test with a few free DNS resolvers that were supposed to block access to phishing and malicious domains.

In summary: they did not work as expected. To be fair to them, my testing was not very scientific as I only got a few random malicious domains from pishtank, malware domains and my email, and expected them to be blocked. So maybe .. that was expected.

However, that got me thinking .. What about our children? If they were not able to block access to malicious domains, would they be able to block access to porn? I assume the majority of people using these services are actually looking to block access to adult content for their kids. Would they at least be able to do a good job there?

Testing Porn Filters (the free ones)

So testing again, I went. I picked up 6 free Porn/Adult/Explicit content filters:

* ( 208.67.222.123 ) *Neustar_FamilySecure ( 156.154.70.3 ) * ( 185.228.168.168 ) * ( 199.85.126.20 ) * ( 77.88.8.7)*AdGuard_Family ( 176.103.130.132)And tried to see if they would be able to block access to porn. I chose 88 different pornographic sites (the first ones ranked on Google & Bing for the keyword "porn"). I pretty much went manually — page by page, getting each domain. After page 6, I skipped to page 15 and kept collecting domains. The reason I skipped to page 15 was to get a few less popular domains. I also re-did the test with two other similar keyword that means "having sexual intercourse" in a less noble ways. That's how I got the .

Results

Out of the 88 porn domains, I expected all of them to be blocked. They were ranked on the search engines and easily found online. Only CleanBrowsing blocked them all, with Norton SafeConnect very close in second place by missing 5 domains:

CleanBrowsing: 100% blockedNorton: 94% blocked (83 blocked, 5 not blocked)Yandex: 93% blocked (82 blocked, 6 not blocked)OpenDNS: 89% blocked (79 blocked, 9 not blocked): 81% blocked (72 blocked, 16 not blocked)AdGuard: 55% blocked (55 blocked, 39 not blocked)

Neustar and AdGuard were not good at all, missing even some of the popular sites. Full table of results is on this link:

Partial screenshot of the pastebin with the results (medium doesn't make it easy to import a table):

Testing free proxies

There are many easy to use free proxies that should be blocked when you are filtering access to pornographic content. When testing the top 10 free proxy domains, only OpenDNS and CleanBrowsing blocked all of them.

None of the other services tried to block access to proxies. I would give them a -1 for making it easy to bypass their own filters.

Forcing Safe Search

One of the things that are important when blocking access to pornographic content is restricting search engines — as they cache porn images on the results, bypassing the filters control.

Google offers a way to force Safe Search via DNS and only Yandex, AdGuard and enforced them. That's a big plus for these 3 services for that.

TLDR

If you got here, you read the whole thing, so that's pretty much it. I didn't test any of the paid services, so can't attest on their accuracy. What else can we test? Suggestions are welcome.