The internet censor systems

James Fallows gives at The Atlantic a thorough write-up of the current understanding of China's internet censorship systems, at least the technical side of this.
How effective this all is - meant to be - remains of course an open question.

Depending on how you look at it, the Chinese government’s attempt to rein in the Internet is crude and slapdash or ingenious and well crafted. When American technologists write about the control system, they tend to emphasize its limits. When Chinese citizens discuss it—at least with me—they tend to emphasize its strength. All of them are right, which makes the government’s approach to the Internet a nice proxy for its larger attempt to control people’s daily lives.