China cut itself off from much of the global internet for just over an hour on Wednesday.<\/p>\n
Activist group Great Firewall Report spotted the outage, which it said<\/a> disrupted all traffic to TCP port 443 \u2013 the standard port used for carrying HTTPS traffic.<\/p>\n \u201cBetween approximately 00:34 and 01:48 (Beijing Time, UTC+8) on August 20, 2025, the Great Firewall of China (GFW) exhibited anomalous behavior by unconditionally injecting forged TCP RST+ACK packets to disrupt all connections on TCP port 443,\u201d the group wrote in a Wednesday post.<\/p>\n That disruption meant Chinese netizens couldn\u2019t reach most websites hosted outside China, which is inconvenient. The incident also blocked other services that rely on port 443, which could be more problematic because many services need to communicate with servers or sources of information outside China for operational reasons. For example, Apple and Tesla use the port to connect to offshore servers that power some of their basic services.<\/p>\n China sometimes cranks up censorship during events it doesn\u2019t want its population to know about. The Register is unaware of any such event that took place during this outage.<\/p>\n Therefore, there\u2019s no obvious reason China decided to block port 443.<\/p>\n The Great Firewall Report thinks the device that implemented the block \u201cdoes not match the fingerprints of any known GFW devices.\u201d<\/p>\n The group therefore thinks the incident \u201cwas caused by either a new GFW device or a known device operating in a novel or misconfigured state.\u201d So perhaps China was either testing its ability to block port 443 \u2013 which Beijing might see as a useful capability \u2013 or someone messed up.<\/p>\n This is not the Great Firewall\u2019s first glitch. We\u2019ve seen it leaking a little info<\/a>, and leaving itself open to attack<\/a>. China\u2019s overall censorship regime is also imperfect, due to both technical and bureaucratic<\/a> bungling.<\/p>\n