The Great Firewall of China: IP Blocking at a National Scale

Introduction: The Digital Border

The internet was designed to route around damage, but what happens when the 'damage' is deliberate censorship by a government? The Great Firewall of China is the largest and most sophisticated IP filtering system on Earth. It analyzes and controls the data of over a billion people.

How the Wall Works

It isn't just one firewall; it is a multi-layered system. First, it uses **IP Blacklisting** to automatically drop traffic sent to known IPs (like Facebook or YouTube servers). Second, it uses **DNS Poisoning**, meaning if a citizen types `google.com`, the phonebook lies and sends their browser to an empty IP address instead.

Conclusion

The Great Firewall proves that while the internet is conceptually free, the physical infrastructure (the cables and routers) can still be entirely controlled by those who own them. Check the status of global routing here.