How to Tell if a Domain Name Is Blocked by GFW of China
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1. What is China Block?
China block refers to the blocking of website content by the Great Firewall, also known as the “GFW” or “Great Firewall of China.” It can involve the censorship of website content or the blocking of server communications.
The Great Firewall (GFW) originated in 1998 and was designed to monitor and the contents exported by foreign Internet as they enter the Chinese network environment. Contents that do not meet the requirements of the Chinese government are interfered, blocked, and restricted. As Internet censorship in China is extensive, Chinese websites with contents that are deemed inappropriate are requested by the government to modify the website contents; any publication or update to the contents must first undergo self-censorship and supervision, and some websites are even directly masked or blocked. The GFW is mainly to monitor and analyze the access of all network resources outside the border of China; any website information deemed illegal, sensitive, or unfavorable to the nation as a whole, will be directly masked or blocked by the Chinese government. Examples of commonly blocked targets include Facebook, Google, Telegram, Twitter, illegal websites related to pornography, gambling, drugs, as well as websites with politically sensitive information.
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2. How to Determine If a Website Is Blocked by GFW?
There are many third-party testing tools available online for checking if a website is blocked. Simply search for “Great Firewall Test” and you will find numerous detection websites and simulated access tools. In the following article, we will use the “Boce” testing tool as an example for demonstration.
【Boce】(https://www.boce.com/): this tool has many nodes in various parts of China. We take the domain and test the results of access at various nodes of “Boce” website.
Being “blocked” can generally be divided into the following two situations:
A. Domain Name Block
It refers to the domain name being blocked by the Great Firewall of China, which makes it inaccessible when accessed within China but accessible outside China.
B. IP Block
It refers to the IP address being blocked by the Great Firewall of China. The difference between IP block and domain name block is that when an IP address is blocked, all domain names associated with that IP address will be inaccessible within China, but accessible outside China.
The results of these two types of blocking may appear similar when tested with third-party tools. Regardless of the type of blocking, it is important to double-check. Cross-referencing can be used to compare the information of a healthy domain with the suspected blocked domain or blocked IP for further assessment. With various possibilities in the online world and the intervention of the Great Firewall of China, confirming domain issues becomes more complex. It is recommended to use multiple third-party tools to improve the accuracy of judgment. The following section will introduce some simple preliminary judgment methods.
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3. Demonstration and Explanation through Practical Testing
A. Domain Name Blocked
Step 1: First, find healthy domain name that can be normally accessed in China, one with the correctly responded HTTP Code in the “Status” column. Next, we will use the following domain names for case explanations and cross-referencing tests.
Healthy domain: goodexample.com
Resolved IP: 123.123.123.123
Step 2: Use Boce to check the domain, the Status column of most regional nodes return a message of 000, indicating the normal http code 200 is not obtained and the access is abnormal.
Example of blocked domain: badexample.com
Resolved IP: 234.234.234.234
Step 3: An IP address of a healthy domain (123.123.123.123) is bound to specified resolution; however the status code still displays 000, which means the domain cannot be normally accessed even with a healthy IP. In this case, we can determine that the domain badexample.com has been blocked.
Step 4: The test can be done in a reversed way, in which a healthy domain goodexample.com is tested with a resolved IP (234.234.234.234) suspected of being blocked. The results showed that the IP of the suspected blocked domain is good and can return a status code normally.
B. IP Blocked
Step 1: First, find a healthy domain name that can be accessed normally in China. Then, we will use the following domain names for case explanations and cross-referencing tests.
Healthy domain: goodexample.com
Resolved IP: 123.123.123.123
Step 2: When using Boce to test the domain, most of the “Status” fields in different regions’ nodes show “000,” indicating that it is unable to obtain the HTTP code 200 message and establish a connection.
Example of blocked IP: badexample.com
Resolved IP: 321.321.321.321
Step 3: By binding the IP address 123.123.123.123 of a healthy domain for resolution, we can obtain the status code successfully, indicating that using a different healthy IP domain allows us to access the website. In this case, we can determine that the IP address 321.321.321.321 being used for the domain example.com is blocked.
Step 4: Test again in the opposite way, use the blocked IP address (321.321.321.321) to specifically resolve the healthy domain goodexample.com. We can see that the domain that was previously accessible cannot normally returns status codes after binding to a blocked IP address.
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C. Blocked by Specific Telecommunication Vendors
In addition to being inaccessible in all regions of China, there is another situation where a domain is blocked by a specific telecommunications provider. China has three major telecommunications providers: China Telecom, China Unicom, and China Mobile. This type of blocking by a telecommunications provider is more common with China Mobile.
From the example in the above image, it can be observed that the China Mobile route consistently shows abnormalities. In such cases, selecting “Mobile” directly through filtering provides a clearer view. Even after changing the IP and retesting, the status still shows 000. This situation is referred to as “domain blocked on the mobile network.” However, customers using China Telecom or China Unicom networks can still access the domain normally.
Solutions to Being Blocked:
[Domain Blocked]
- Abandon the old domain and register a new one to use.
- Check the website content, remove any sensitive information, and move the blocked domain to China, using Chinese servers and completing the record-filing process.
[IP Blocked]
- Request the provider to change to a functioning IP.
- Wait for the IP to be unblocked.
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