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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星期一, 1月 26, 2015

给鲁炜和中国网信办的公开信

2015年1月26日

中国,北京。

鲁炜先生:

在2015年1月22日, 您领导的中国网信办对我们发表的Outlook在中国遭中间人攻击的文章进行了公开回应。 在中国网信办的公开回应中,您的同事姜军说我们的指责是“无端臆测,纯属境外反华势力的造谣和污蔑“。

我们GreatFire.org成员对中国网信办的评论非常愤怒,我们在本公开信中逐条驳斥。

我们没有轻易指责中国网信办。我们收集了大量数据来支持我们的结论。很多报告都支持了我们的分析,包括了截图许多中国网民的报告和其他技术人员的独立分析

我们之前报道过对iCloud,雅虎,微软和谷歌进行的中间人攻击,每个公司都确认了中间人攻击的真实性。我们还邀请了其他技术人员对攻击数据进行了独立分析。 你可以阅读对每次攻击的独立分析: OutlookiCloud谷歌雅虎Github 。 每个分析结论都类似:

星期一, 1月 19, 2015

Outlook在中国遭中间人攻击

网络监测组织GreatFire于1月17日收到了报告,指微软电邮系统outlook在中国遭中间人攻击(MITM)。此次攻击针对通过移动设备上的邮件客户端收发outlook邮件的人士。该组织怀疑,此次攻击是审查部门在测试防火墙技术。

当中国用户通过电子邮件客户端(Ice-dove)进入outlook时,可看到以下证书:

Greatfire的测试证实了outlook确实遭到攻击:IMAP(交互邮件访问协议)与SMTP(简单邮件传输协议)都遭受了中间人攻击。但网站界面(https://outlook.com 和 https://login.live.com/)没有受到影响。这次攻击持续了大约一天,现在已经停止。

这种形式的攻击尤其狡猾:相比于通过浏览器,用户通过电子邮件客户端所接收到的警告非常不明显,更容易被忽略。如下图:

(从iphone默认电邮客户端接收到的错误样本)

当客户端试图自动检索信息时,用户只能看见一个突然弹出的警告。因为用户没有主动检索信息,大多数的用户在点击“继续”之前不会细想,却忽视了警告信息、或把警告信息归咎于网络连线的故障。如果用户真的点击了“继续”,他(她)所有的邮件、通讯录、密码都会被黑客所窃取。

星期五, 1月 09, 2015

GFW升级导致用户被“墙”到色情网站

网络审查监测组织Greatfire指出,中国的防火墙日前进行了升级,加入新的“墙”法,导致用户甚至被墙到色情网站。此次升级也导致许多翻墙工具失效。

此前,中国的网民在未使用翻墙工具的情况下,若要连接Facebook,Twitter和其他被封的网站,会被域名服务器污染系统导到一系列被封锁、或根本不存在的假IP地址。然后,用户将跳转到连接超时的页面。

但中国的域名服务器污染系统升级之后,在原有假IP地址的基础上,审查机构开始使用有相应网站的真IP地址。例如,https://support.dnspod.cn/Tools/tools/ 显示,如果中国网民试图在国内连接Facebook,用户可能登入一个随机的页面,如http://178.62.75.99

一位中国网民向Greatfire报告说,当他从中国连接Facebook时,他竟然连到了一个俄罗斯的网站,且完全与Facebook无关。另一位用户在推特上表示,当他试图连接一个VPN网站时,他被导到一个德国的成人网站。

在中国强力扫黄的大环境下,用户被导到成人网站,显得尤其讽刺。北京经常将“保护未成年人”作为网络审查的一个说辞。但在这个例子上,当用户想连接一个合法但被封锁的网站时,却被返回到被中国视为违法的成人网站。如果这不是审查方出错,是否意味着中国的审查机构是超越中国法律的?

此次中国的防火墙升级,有效地导致许多反DNS污染的工具失效。由于GFW此前仅适用小量的假IP,这些翻墙工具可容易跳过这些假IP,并绕过封锁连接到正确的IP地址。但由于现在GFW也使用有效的IP地址来进行污染,这样的翻墙原理也随之失效。

这也可能意味着,审查机构可能在试验新的隐藏审查的方法,通过将网民导到随机的可连接的页面,让用户以为是原网站出了问题。

中国网民对于连接超时并不陌生,许多人自然而然地将其与墙联系起来。Greatfire认为,当局可能希望,在一段过渡期后,网民将适应新的DNS污染模式。中国的许多网络服务提供商此前已经使用这种重新导向随机页面的方法,来向用户推送广告。

很显然,当局在不断地修补升级审查机制。Greatfire预期,在今后几个月内,GFW将有更多的变化。


星期三, 12月 31, 2014

CNNIC leadership change coincides with blocking of Gmail

On December 26, 2014, in an announcement posted on their website, a new chairperson for CNNIC was directly appointed by the Cyberspace Administration of China. The announcement of this appointment coincided with the complete blocking of Gmail.

Cyberspace Administration of China (中央网信办) is chaired by Lu Wei, “China’s web doorkeeper”. Lu Wei is also the vice chair of the Central Propaganda Department, according to his official resume.

chair.png

This office is directly responsible for the blocking of Gmail and other websites including Facebook, Twitter and Google.

CNNIC is China’s certification authority and operates the country’s domain name registry. 

What are certificates used for?

Certificates are used primarily to verify the identity of a person or device, authenticate a service, or encrypt files. 

What is a certification authority (CA)?  

星期二, 12月 30, 2014

Gmail completely blocked in China

All Google products in China have been severely disrupted since June of this year and Chinese users have not been able to access Gmail via its web interface since the summer. However, email protocols such as IMAP, SMTP and POP3 had been accessible but are not anymore. These protocols are used in the default email app on iPhone, Microsoft Outlook on PC and many more email clients.

On December 26, GFW started to block large numbers of IP addresses used by Gmail. These IP addresses are used by IMAP/SMTP/POP3. Chinese users now have no way of accessing Gmail behind the GFW. Before, they could still send or receive emails via email clients even though Gmail's web interface was not accessible. 

Google's own traffic chart shows a sharp decline of Chinese traffic to Gmail. 

Below is a ping request to the Gmail SMTP server, which is completely inaccessible in China.

 

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