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 65.49.2.178. 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 http://65.49.2.178, which didn’t respond during that time.  The overwhelming traffic to this IP likely crashed the server.

Timeline

Event

15:15

GFW DNS poisoning begins. First recorded instance.

15:17

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.

15:39

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

16:00

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 65.49.2.178. This could explain why DNS servers in China were poisoned. However, during that time, we see that a lookup to 8.8.8.8, 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 65.49.2.178 could only have been returned by GFW.  If the Chinese root DNS server was hacked, a DNS lookup in China via 8.8.8.8 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. 65.49.2.178 is owned by Dynamic Internet Technology according to an IP lookup, and they are behind the famous circumvention tool FreeGate. Currently, http://65.49.2.178 is a mirror site for dongtaiwang.com, a news portal operated by Falun Gong groups.

Blocking 65.49.2.178

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

Hackers

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, 65.49.2.178 during that time was not serving any content and with such traffic, it looks more like a DDOS attack agasint 65.49.2.178. They couldn't use that IP to spread sensitive content during that time. However, from today, they have indeed started to use http://65.49.2.178 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, 2月 18, 2016

From the desk of Lu Wei: Apple, encryption and China

Lu Wei, Director of the Cyberspace Administration of China, offers some friendly help to FBI Director James Comey.

星期四, 9月 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.

星期三, 9月 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 http://adcdownload.apple.com/Developer_Tools/Xcode_7/Xcode_7.dmg to download Xcode.

星期一, 9月 21, 2015

中美互联网论坛回信

你们的公司有责任尊重人权,防止您的业务被侵犯。我们知道,中国是你们公司的一个重要市场,但恳请您在美国促进和保护人权的同时,也同样在中国致力于此。习主席的访问和美中互联网产业论坛是一个理想的机会,明确表示你的公司将会捍卫隐私权,反对成为监控同谋,将它们的强大在中国和美国一视同仁。

星期六, 9月 19, 2015

中国流行的iOS应用遭到前所未有的恶意软件感染

发生了什么?

 

据最近的报道,中国开发者使用的某些版本的Xcode被感染,在开发者不知情的情况iOS应用中就被注入了用于跟踪的代码。(1、2)。被注入后,开发者们将他们被感染的iOS应用程序的上架了App Store并得到苹果批准。截止完稿前,这些被感染的应用在App store仍可访问(外部链接)。任何安装并启动了这些被感染应用的用户都将是追踪代码的受害者。

 

这是苹果应用商店一次重大的感染事件。苹果以人工审查所有的被提交应用而著名,相对Android商店的恶意软件会更多。这是苹果应用商店历史上最广泛和重大的一次恶意软件事件传播事件。

 

这些被感染Xcode被托管在百度云上。百度本身似乎并没有意识到这些Xcode是被感染的。在这次事件逐渐浮出水时该公司于昨日删除了这些被感染的文件。由于在中国下载外国网站的文件时速度非常慢,许多中国人希望能够从国内网站来下载。很多人也会使用下载软件,如迅雷,而不是直接从官方的Mac App Store中下载。

 

据用户的报告,许多中国著名的应用受到影响。我们在下面的列表中链接了测些受感染的应用,但请不要下载他们,我们只是链接他们,目的是使用户能够知道具体是哪些应用程序。这些受影响的应用程序包括:

 

微信(link is external) 中国最流行的聊天应用

网易云音乐(link is external) (NetEase Cloud Music) - 网易的免费音乐应用

网易公开课(link is external) (NetEase) - 被许多学生所使用的公开教育应用

中信银行动卡空间(link is external) (China CITIC Bank Card Space)

中国联通手机营业厅(link is external) (China Unicom Shop)

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