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[liberationtech] Images of Blocking in Different Countries?

Philipp Winter philwint at
Wed Aug 15 15:10:39 PDT 2012

On Thu, Aug 16, 2012 at 05:15:49AM +0800, Eric S Johnson wrote:
> I.e. it's easy to register a new domain (call it
> and put up onto it a handful of pages which include every possible word and
> phrase which we know are problematic to the Chinese censors. Start with the
> list of words which trigger censorship and surveillance in TOM Skype (the
> wordlist's been repeatedly cracked by researchers at, I think, Arizona). Add
> all the content which the good folks at UC-Berkeley’s China Digital Times have
> detected cause immediate censorship on Weibo (China’s Twitter-like service).
> This should be a total of about 400 words and phrases (almost all only in
> Chinese).
>                Then access those pages from within China.
>                As far as I can tell, access will be unimpeded.

Ah, thanks for the explanation. I understand now. Keywords can be filtered in
two directions. From the client to the server (GET request filtering) and the
other direction (inside the HTML text sent back).

While GET request filtering is still ongoing, it looks like the HTML response
filtering (from the server to the client) was indeed discontinued. The paper
"Empirical Study of a National-Scale Distributed Intrusion Detection System" [1]
looks at that in more detail.

>                But my own tests have been unscientific, i.e. not conducted over
> a variety of ISPs, times, and content. It would be interesting (and not
> difficult) to do this more rigorously.

Quite interesting to read though, thanks!



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