Mystery in China, which has disconnected one hour from the global internet for an unknown reason
People checking their phones in front of one of China's scholarships, photo: May James / Zuma Press / Profimedia Images
The “Great Chinese Firewall”, the wide censorship system of the Internet implemented by Beijing, seems to have recorded a problem that has led to disconnecting the country from most of the global internet on Wednesday, reports The Register.
The interruption was observed by a group of activists called “Great Firewall Report”, which states that all the traffic to the TCP 443 port – the standard port used for Internet connections.
“Between about 00:34 and 01:48 (Beijing time), on August 20, 2025, the great Firewall of China presented an abnormal behavior, injecting unconditionally packages TCP RST+ACK Forged to disturb all the connections on the TCP 443 port, ”the group wrote in a public message.
In computer networks, communication by TCP (“Transmission Control Protocol”) is done through packages containing a “header” (header) with various “flags” (ticks) that show the condition of the connection. Two of these flags are: RS (Reset) that signals that a connection must be closed immediately. It is used when something does not work well (for example, the server rejects the connection); Ack (“AcknowledGment”) – confirms the receipt of the data. Almost all the packages after the connection contains the ACK.
The transmission of packages TCP RST+ACK It is a way to suddenly close a connection, and the firewalls or censorship on the Internet use this technique to block traffic.
Until the Internet did not just do the websites outside of China unavailable
This disturbance meant that Chinese Internet users could not access most of the sites hosted outside China. The incident also blocked other services based on port 443, given that many services must communicate with servers or sources of information outside China for operational reasons. For example, Apple and Tesla use the port to connect to external servers that feed some of their basic services.
China sometimes raises the level of censure during events that she does not want the population to find out like the anniversary of the Tiananmen Square. But in this case there is no clear reason why the Beijing authorities wanted to interrupt the connection to the global internet.
Great Firewall Report He believes that the device that has implemented the blocking “does not match the digital fingerprints of any well -known device of the great Firewall”, the censorship system of Beijing.
The group believes, therefore, that the incident “was caused either by a new device, or by a device already known in an unusual or configured state.” Therefore, it is possible that the Chinese authorities may have tested their ability to block port 443 or as a person responsible for managing the system has made a mistake.
A problem with the Internet was recorded in Pakistan a few hours before
The Tech The Register site notes, in the absence of a conclusive explanation, that it is not the first time that the great Firewall of China would have failed that the general censorship regime of Beijing is imperfect, both due to technical and bureaucratic errors.
However, it is believed that China secretly shared the technology behind the great Firewall with other nations.
The register journalists mention this because it is believed that Pakistan has implemented its own version of Firewall and, according to the Netblocks Internet monitoring company, has experienced a massive decrease in local internet traffic a few hours before the incident related to Port 443 in China.
