Most dns servers don't allow zone transfers, so I don't believe you'll be able to enumerate domains like this.

In general enumerating domains is not really possible (you can't just dump all North Korean domains for example, and people have tried).

I'd start by figuring out how they are blocking sites. Probing to see which IPs are blocked would be much easier. There are various tools to lookup which sites are hosted on a given IP address (using crawled data).

One way to do this would be to try connecting from outside Pakistan (e.g. EC2 server) and from inside and seeing if a IP is blocked.

Scanning all 4 billion IPs surprisingly doesn't take too long on a modern internet connection.

My two cents: Don't do it on your own. Contact NGOs that work on the censorship issues, EFF, AccessNow, FLD, etc.. They have been working on these issue for a while and probably can help you with their resources.

I might after I build the site :)

I think you should crowd source it. Build a simple two-page site where people can submit censored websites and another where you display them. But your very own website could end up on the list.

That is a wonderful idea!

I own https://www.DomainDetect.io, we pull new domains from Zone files/3rd party sources daily. ~200,000-400,000 domains per day to alert on new phishing sites for businesses. So we do something similar. I would start with something like https://czds.icann.org/en attempting to resolve them asyncronously in your country, then work your way through the new daily additions. Use an ElasticSearch/Cassandra backend for speed to query that volume of information.

Your problem will come from the countries/TLD's that dont play ball with their zone files. These are trickier to obtain.

Yours will soon be on that list.

I'd like to see that happen. I don't take kindly to being censored arbitrarily and will fight tooth and nail to the full extent of the law :)