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英文原文来自 https://blog.torproject.org/blog/learning-more-about-gfws-active-probing...

Roya, David, Nick, nweaver, Vern, 和我刚刚完成了关于GFW主动探测系统的研究。这个系统在几年前就被用来探测翻墙工具，比如Tor。我们在之前的博文中介绍过GFW主动探测系统是如何工作的。但有几个问题我们没有回答。比如这个系统的物理结构是怎样的。那些用来主动探测的IP是归GFW所有的么？ 有猜测GFW短时间内劫持了部分IP来用来主动探测，但没有证据。这次研究回答了这些问题。

因为这个实验是网络检测，我们从收集数据开始。我们创建了3个数据库，包括了GFW主动探测的小时/月份/年份的数据。这3个不同时段的数据库让我们从不同角度了解GFW主动探测的工作原理。我们公开了其中的两个数据库，你可以重复我们的实验，或者自己分析。

• 通常来说，如果Tor的某个网桥代理被GFW检测并封锁，它会一直被封锁。但是这意味着网桥代理完全无法访问吗？ 我们让中国的VPS一直连接我们控制的网桥代理。我们发现，每25小时，中国的VPS可以短暂的连接到我们的代理网桥。下图显示了这个现象。每个数据点表示中国的VPS试图与网桥代理建立连接。中国联通和中国教育网都有这个周期性现象。有时候，网络安全设备在更新规则时会默认允许所有流量，但我们不知道GFW周期性现象是不是因为这个原因导致的。

• 我们找到了规律，GFW主动探测的TCP头暗示那几千个IP都来自与同一个地方。下图显示了数据包的初始序号和时间。每个数据点都是一个主动探测连接。如果每个主动探测都是从不同地方发出的，我们应该看到随机的数据点，因为数据包的初始序号是随机选择的。但是下图显示主动探测连接虽然来自不同IP，但是非常有规律。我们认为主动探测的初始序号是按照时间产生的。

 

• 我们发现GFW主动探测不仅仅针对了Tor。GFW还对 SoftEther 和GoAgent进行了主动探测。这说明主动探测系统是模块化的。GFW工程师能比较简单的对新翻墙软件改进主动探测功能。

We have been critical of Wikipedia’s approach to censorship in the Middle Kingdom. In a recent piece for the Huffington Post, I lamented the loss of Wikipedia in China. The encyclopedia’s founder, Jimmy Wales, who is also a staunch and public anti-censorship champion, reached out to us on Twitter. Jimmy agreed to publish our unedited exchange on the difficult nature of dealing with censorship in China.

What happened?

ShawdowSocks

On August 22, an open source project called ShadowSocks was removed from GitHub.

According to the project’s author, the police contacted him and asked him to stop working on the tool and to remove all of the code from GitHub.

He later removed the reference of the police, presumably under the pressure of the police.

After the news, many Chinese and foreign developers, as well as ShadowSocks users, paid tribute to the author. As a result of this attention, ShadowSocks became the top trending project on GitHub.

 

When LinkedIn decided to create a China-hosted version of its website in February, 2014, it made a decision to compromise the company's values in the pursuit of the dollar.

It's important to note that before LinkedIn launched LingYing (the local version of the site), LinkedIn was already active in China. By their own account, they had four million registered users (with little marketing effort), a Chinese-language interface and China-based clients who were buying recruitment ads on the platform (the major source of their revenue). The site had been blocked by the authorities for one 24-hour period but otherwise was always accessible.

So why was it necessary for LinkedIn to create a local entity in China? With a local entity the company would be able to issue official receipts in RMB, making it more convenient for local companies to buy advertising on the site. A local entity also makes it easier to secure marketing deals to promote LingYing in China.

But perhaps the biggest appeal in creating a local entity for LinkedIn is that it would be among the few foreign internet companies who could cosy up with Lu Wei and the Cyberspace Administration of China (CAC). Having that kind of a relationship with CAC surely helps the business and those who are associated with the company.

Wikipedia is the latest nail in the internet freedom coffin and it certainly will not be the last. Wikipedia thought that by engaging with China, the authorities would gradually open up. They thought that by allowing the Chinese authorities to censor as much information as they wanted, that eventually they would relinquish control. They thought that for those in China, having access to some Wikipedia pages was better than having access to none.

On April 1, 2015 Google announced that they will no longer recognize the CNNIC Root and EV (extensive validation) certificate authorities (CAs).

On April 2, 2015 Mozilla concluded that CNNIC’s behaviour in issuing an unconstrained intermediate certificate to another company was ‘egregious practice’ and that Mozilla products would no longer trust any certificate issued by CNNIC’s roots. Mozilla also published a more detailed report about their actions.

After unauthorized digital certificates for several Google domains were exposed by Google and Mozilla on March 23, 2015, CNNIC censored any mention of these posts. CNNIC is not only a certificate authority, they are also China’s online censorship apparatus. CNNIC was, is and will continue to practice internet censorship.

 

News about the April 1 and 2 annoucements has again been censored on social media and also on traditional media in China.

Below is a screenshot of Weibo posts about these announcements.

 

The Great Firewall has switched from being a passive, inbound filter to being an active and aggressive outbound one. This is a frightening development and the implications of this action extend beyond control of information on the internet. In one quick movement, the authorities have shifted from enforcing strict censorship in China to enforcing Chinese censorship on internet users worldwide.