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Comment by sehrope | Hacker News Reader

> Any request that is denied by OpenDNS is then allowed by our DNS server, and any request allowed by OpenDNS is blocked by us.

The most interesting part of this to me is using multiple DNS providers to determine which category the site is in. It's both simple and effective.

If they actually go ahead with this plan in the UK and it's implemented similarly (eg. via DNS rather than IP blocking), somebody should make a list of what's blocked. Go through the top N sites and for each run a DNS lookup from both a filtering DNS server and also a couple non-filtered ones (ex: Google DNS[1]) then compare the results[2].

Bonus points if someone builds a way to crowd source the data so that it gets logged from multiple DNS servers round the world.

[1]: https://developers.google.com/speed/public-dns/

[2]: This would need to do more than a plain A == B as each address could resolve to multiple IP addresses.

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They can't and don't do it with just a DNS, it'll have to be DNS + HTTP URL. Otherwise porn hosted on one large shared hosting would block everything. (e.g. imagine if the Amazon EC2 DNS got blocked).

The current UK ISP filter (the one that already filtered Wikipedia), used DNS & HTTP. IP addresses that needed filtering were redirected to their HTTP server by sending back their IP address, and then a HTTP proxy was used to filter specific URLs. This allowed them to block certain URLs. It was initally detected because lots of wikipedians noticed a lot of edits (basically lots of the UK) coming from a small amount of IP addresses (the IP addresses of the proxies)

They CANNOT use HTTP filtering as that would break on HTTPS.

Nope, the domain is always visible on HTTPS, due to SNI. They can just block it.

Older Win XP machines doesn't support SNI, so you could get around it with an older machine. Of cause that's a problem that will go away over time.

To connect to an HTTPS site without SNI, the IP can only host a single domain, so they can just block the whole (IP:443) combination without affecting any other site.

What if the IP is dynamic? Say an Azure Cloud Service.

I think the problem is that you'd need a different X.509 certificate for TLS, for each and every single IP.

The certificate is issued for the domain, not the IP.

I think Cleanfeed didn't block HTTPS. When have you ever heard of a public, governmental programme that didn't have a stupid flaw? :P

Yeah, and he government would never make that mistake…

http://www.smh.com.au/technology/technology-news/how-asics-a...

The Danish Internet filtering works by messing with the DNS at the ISP level. If you don't want to get filtered, just switch to a non-ISP DNS, or run your own. Sadly it was implemented with little or no public debate, very very few got upset and most of us just switch DNS. I think the UK is in a much better position because they at least have the debate public and loud.

I was actually also admiring the simplicity of his solution, to take advantage of services that are already in place doing the exact opposite of his.

Tip of the hat to the author...

Cleanfeed (the UKs child porn filter) is supposed to be IP blocking/NAT based, coupled with web proxies. Given the scope of the filtering this time around though, it may be done by DNS. Let's hope so.

I remember when they used this system to block an image on Wikipedia. Much hilarity ensued: http://wiki.openrightsgroup.org/wiki/Cleanfeed#Wikipedia_.2F...

> Bonus points if someone builds a way to crowd source the data so that it gets logged from multiple DNS servers round the world.

What you want is a website that answers: Does Country-C block Website-W? A user gives it a URL and it has VPNs surfacing in lots of different countries and it tries them all, and displays in which countries the URL is blocked.

The website also stores and records all blocked/unblocked websites, and allows this data to be downloaded.

There is something like that for the great wall of china: http://www.greatfirewallofchina.org/

Yes. Although that site keeps no history, doesn't allow you to download a list of blocked sites, and only works for China.

And it bizarrely replaces its headers with Flash.

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