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 pos

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.