New Version of

We are very pleased to unveil a new version of today. Here are some things we've been working on in an effort to improve the web site and to bring transparency to online censorship in China. 

Real Time Testing 

You can now test whether any URL is blocked or restricted in China in real time. Just enter any website in the main search field on the top of this page and click Test Now. Or, when browsing a report on a particular URL, you can request to have it retested immediately by clicking Test Now on its page. This is the first time that real-time monitoring of key words in China has ever been publicly available. Other web sites share information about key words which may have been blocked in the past but which are now unblocked (or vice versa). Our real-time service will allow visitors to the site to monitor blocked key words in relation to breaking news stories in China. Visitors will also gain insight into anomalies that sometimes occur with the Great Firewall including the ability to see if blocked sites like Facebook and Twitter happen to be open in China for short periods of time. 


We now report blocks and restrictions as percentages over the last 30 days. For example, if a URL has been tested 10 times in the last 30 days, and as a result of those tests the connection was reset 5 times and the download speed was slower than 5 kbps 2 times, our report would state that the web site is 50% blocked (5 /10) and 20% otherwise restricted (2 / 10). This means that our reports will be more reliable by providing more information about how exactly these sites are being blocked or throttled. There are frequent glitches in the Great Firewall and the previous version of our website reported only on the latest status of a web site, which could give distorted impressions. 

To qualify as a Website Blocked By The Great Firewall of China or a Search Blocked By The Great Firewall of China a URL has to have been blocked at least 50% in the last 30 days. 

Types of Censorship 

Rather than just reporting a URL as blocked, we now use algorithms to try to deduce the technical type of censorship that is occurring. Current categories are Connection Reset, DNS Poisoning, Redirected To China, Self-Censorship, Throttling and Timed Out. For any given URL, you can click on the days in the calendar to view details on how the URL was determined to be blocked or restricted. More info in our new FAQ

Baidu Self-Censorship 

Last but not least, we now also track Baidu Self-Censorship. We do this by checking for the existence of a self-censorship admission message shown on Baidu for certain sensitive keywords. Please try it out and let us know what you think on info at greatfire dot org or by commenting on this site. Historically, information which appeared about the Great Firewall has focused on what web sites are blocked to users in China, Frequently, this information focused on either popular web sites (like Facebook and Twitter) or on organizations which China has deemed to be detrimental to the people of China. For the first time, we are providing insight into what information is blocked on the biggest search engine in China. Internet users in China for the most part are aware of the fact that large web sites like Facebook are blocked. Our new feature now gives users in China a view on what Chinese keywords are being blocked on Baidu.

We have many more features to add, and you can help us in this process. Please add comments on any page with suggestions on what we can do better or problems we need to fix. Let's work together to bring transparency to online censorship in China.


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Thu, Sep 24, 2015

Apple blocked CNNIC CA months after MITM attacks

In March of this year, Google found unauthorized digital certificates for several Google domains. The root certificate authority for these domains was the China Internet Network Information Center (CNNIC). CNNIC was controlled by the Chinese government through the Ministry of Industry and Information Technology and is now under the management of the Cyberspace Administration of China (CAC). CNNIC was recognized by all major browsers as a trusted Certificate Authority. If CNNIC signs a fake certificate used in a man-in-the-middle attack, no browser will warn of any unusual activity unless the certificate is pinned.

Wed, Sep 23, 2015

Malicious Xcode could spread via download manager Xunlei

What’s at stake?

We reported last week that popular Chinese iOS apps were compromised in an unprecedented malware attack. We discovered that the source of the infection was compromised copies of Xcode hosted on Baidu Pan. Apple has published an article urging developers to download Xcode directly from the Mac App Store, or from the Apple Developer website and validate signatures. We’ve now discovered that even if a developer uses a download link seemingly from Apple, he might still be possible to obtain a compromised copy of Xcode.

Please note that we do not have evidence that such attacks has happened. But it is an easy attack that anyone can implement.

How does it work?

This compromise happened because of Xunlei. Xunlei is the most popular download manager in China. Much of its popularity is due to the fact they can accelerate download speeds by pulling resources from other Xunlei users as well as cached copies on the Xunlei server. All of this, however, is invisible to users. Users can simply enter a regular http download address into Xunlei  download manager and the download will start. Chinese developers were using direct download addresses such as to download Xcode.

Mon, Sep 21, 2015



Sat, Sep 19, 2015

Popular Chinese iOS apps compromised in unprecedented malware attack

What happened?

According to recent reports, some versions of Xcode used by developers in China have been compromised and are being used to inject tracking codes in iOS apps without developer knowledge. (1,2). Unaware of the injection, those developers then released their compromised iOS apps to the App Store which were then later approved by Apple. At the time of writing this post, the compromised apps are still available in the App store. Any user who has installed and launched these compromised apps will be a victim of these tracking codes.

This is a significant compromise of Apple’s app store. Apple notoriously manually reviews all app submissions and, in comparison to Android stores, has been relatively malware-free. This is the most widespread and significant spread of malware in the history of the Apple app store, anywhere in the world.

The compromised version of Xcode was hosted on Baidu Pan. It is unlikely that Baidu was aware of the compromised version of Xcode. The company removed the files yesterday when news of the compromise surfaced. Because of slow download speeds from foreign websites in China, many Chinese developers prefer to download apps from domestic websites. Many Chinese also use download software like Xunlei, rather than downloading directly from the official Mac App Store.

According to users reports, many prominent Chinese apps are affected. We have included links to the compromised apps in the list below but DO NOT DOWNLOAD these apps. We are simply linking to them so that users can recognize the apps. Affected apps include:  

Wechat The most popolar messaging app in China 

Wed, Sep 16, 2015



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。


  • 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。


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New design is great, i love it. Hope it will help people to know greatfire ! (i've made a site about vpn services in the world: )

Best article I've seen so far in this topic!

GreatFire is clearly leading the way in the cat-and-mouse game to escape great firewall of China censorship.

Just one word : PKG, Please Keep Going!!!

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