[regecks]

How? 4chan use Cloudflare. They don't have a dedicated IP, do they?

I would be surprised if Optus actually managed to do SNI filtering for the entire country without screwing it up.

Edit: Huh, seems like they do have a dedicated IP. At least both Robtex and Securitytrails report them as the only tenant on their IP. But you can /etc/hosts 4chan.org to a different Cloudflare IP, and CF will still SNI-route it to the real site. That would defeat any IP address-based block.

[codedokode]

If I remember correctly, Cloudflare assigns different IPs to different sites, so you can use blocking by IP, but of course in this case you will also block other sites using the same Cloudflare server.

I have also written how the site can try to bypass the blocking: https://news.ycombinator.com/item?id=19552689