Internet outage in China on Jan 21

Yesterday we witnessed one of the largest Internet outages ever in China. We have three theories about why this outage may have occurred - two related to the Falun Gong but our third theory is that the Chinese authorities set out to attack our unblockable mirror websites.

From 15:30 to 16:30 (China time) on January 21, DNS lookup to any domain would incorrectly resolve to Websites inside and outside of China were affected. Even Baidu and Sina were inaccessible. Only software using IP directly (e.g. QQ, VPNs) worked during that time. Attempts to visit any website redirected to, which didn’t respond during that time.  The overwhelming traffic to this IP likely crashed the server.




GFW DNS poisoning begins. First recorded instance.


Local DNS servers began to cache incorrect responses. Some large websites in China began to be affected e.g Sina Weibo.


Incorrect DNS continue to spread through Chinese DNS servers. Major websites including Baidu, Sina affected.


DNS poisoning lifted by GFW. But local DNS resolvers cached incorrect responses. Users continued to experience outage.


ISPs around China were manually flushing DNS caches and connections were gradually restored.

We have conclusive evidence that this outage was caused by the Great Firewall (GFW). DNS poisoning is used extensively by the GFW. Some articles that have appeared about this outage suspected that the root DNS server in China was hacked and all domains hijacked to This could explain why DNS servers in China were poisoned. However, during that time, we see that a lookup to, a public DNS operated by Google, returned bogus results if the lookup was done from China. In fact, the Google public DNS was not poisoned; the bogus response could only have been returned by GFW.  If the Chinese root DNS server was hacked, a DNS lookup in China via should have returned a correct response. See the below image from Zhihu.

Our testing system is designed to detect these bogus responses by querying non-existent DNS servers outside of China. Any valid response must come via GFW. We indeed observed such behavior during that time on all domains.  

But why did GFW poison all domains and effectively block all website traffic in China?

This action must have been unintentional. is owned by Dynamic Internet Technology according to an IP lookup, and they are behind the famous circumvention tool FreeGate. Currently, is a mirror site for, a news portal operated by Falun Gong groups.


One hypothesis is that GFW might have intended to block the IP but accidentally used that IP to poison all domains.


Many Chinese media stated that yesterday’s outage may have been due to a hacking attempt. The IP is operated by Dynamic Internet Technology, “mortal enemy number one” of the Chinese government. Some are suggesting Dynamic Internet Technology is behind the outage. However, hacking into a root DNS resolver is not enough to cause this outage, as we explained earlier in this post. They have to hack into GFW. If they are indeed capable of doing that, they can accomplish so much more than messing the entire Chinese internet up. In addition, during that time was not serving any content and with such traffic, it looks more like a DDOS attack agasint They couldn't use that IP to spread sensitive content during that time. However, from today, they have indeed started to use to distribute mirrors and stopped within a few hours.

Blocking our mirror sites

Our mirror site for FreeWeibo has attracted considerable attention and GFW has tried multiple times to block us. We automatically rotate backend servers and the GFW automatically scans new URLs and DNS poisons them.  DNS poisoning is not commonly used compared to connection reset. GFW seems to only use DNS poisoning as a last resort when connection reset fails to block a site. Our mirror forces GFW to add hundreds of rule-sets to DNS poisoning daily and perhaps because of this we were responsible for the system crashing. This is supported by the fact that our new backend domains are no longer automatically blocked.

We’re also continuously improving our backends to prevent automatic discovery from GFW. Perhaps the script operated by GFW acquired a “null” domain from us and consequently blocked everything.



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星期四, 11月 30, 2017


苹果对中国区的审查行为敞开了大门 - 但这似乎只是冰山一角。

星期二, 5月 23, 2017

Is China establishing cyber sovereignty in the United States?

Last week Twitter came under attack from a DDoS attack orchestrated by the Chinese authorities. While such attacks are not uncommon for websites like Twitter, this one proved unusual. While the Chinese authorities use the Great Firewall to block harmful content from reaching its citizens, it now uses DDoS attacks to take down content that appears on websites beyond its borders. For the Chinese authorities, it is not simply good enough to “protect” the interests of Chinese citizens at home - in their view of cyber sovereignty, any content that might harm China’s interests must be removed, regardless of where the website is located.

And so last week the Chinese authorities determined that Twitter was the target. In particular, the authorities targeted the Twitter account for Guo Wengui (, the rebel billionaire who is slowly leaking information about corrupt Chinese government officials via his Twitter account and through his YouTube videos. Guo appeared to ramp up his whistle-blowing efforts last week and the Chinese authorities, in turn, ramped up theirs.


星期一, 12月 12, 2016

面对中国,Google 还打算终结网络审查吗?


星期四, 11月 24, 2016

Facebook: Please, not like this

Facebook is considering launching a censorship tool that would enable the world’s biggest social network to “enter” the China market. Sadly, nobody will be surprised by anything that Mark Zuckerberg decides to do in order to enter the China market. With such low expectations, Facebook is poised to usurp Apple as China’s favorite foreign intelligence gathering partner. If the company launches in China using this strategy they will also successfully erase any bargaining power that other media organizations may hold with the Chinese authorities.

星期二, 7月 05, 2016 现在开始测试VPN在中国的速度和稳定性






我们开发速度测试的目的是要真实反映用户的体验。当用户在网站测速时,浏览器在后台会从10个世界上最流行的网站上下载一些资源文件。根据Alexa排名,这些网站分别是Google, Facebook, YouTube, Baidu, Amazon, Yahoo, Wikipedia, QQ, Twitter and Microsoft Live。速度的结果是简单的计算下载文件文件的大小和下载所需的时间。我们同样也会验证下载的文件是否完整。如果文件的内容是错误的或者在40秒内无法完成下载,我们会标记为失败。这个数据被我们用来生成另一个重要指标-稳定性。


我们的第二个指标 - 稳定性 - 是其他的服务通常不会测试的。一个健康的互联网连接应该达到100%的稳定性,除非有人在测试中把网线拔了。但是在中国使用翻墙工具却不是这样。任何时候连接都有可能变得不稳定或十分缓慢。根据请求的大小,最终的地点和代理的方式,一些请求有可能会失败。比较服务的稳定性要比比较速度更加重要。





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