system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do China and other "enemies of the internet" block their citizens' access to the web?

I've heard about the Great Firewall, but how are they able to implement it on every computer?
gpt
The chinese government owns or controls the telecommunication infrastructure of the country.  Essentially, every wire that runs across the land, every ISP that offers service etc. is controlled by the government.  If you control the wires, it's not a big step to install this "firewall" at every point where these wires connect to the wires in the outside-china internet.  (notably...there is nothing to install on local computers, it's all done at the network level.)