China Upgrades Great Firewall To Defeat Censor-Beating TLS Tools

Great Firewall Report (GFW), an organization that monitors and reports on China's censorship efforts, has this week posted a pair of assessments indicating a crackdown on TLS encryption-based tools used to evade the Firewall. The Register reports: The group's latest post opens with the observation that starting on October 3, 'more than 100 users reported that at least one of their TLS-based censorship circumvention servers had been blocked. The TLS-based circumvention protocols that are reportedly blocked include trojan, Xray, V2Ray TLS+Websocket, VLESS, and gRPC.' Trojan is a tool that promises it can leap over the Great Firewall using TLS encryption. Xray, V2ray and VLESS are VPN-like internet tunneling and privacy tools. It's unclear what the reference to gRPC describes -- but it is probably a reference to using the gRPC Remote Procedure Call (RPC) framework to authenticate client connections to VPN servers.

GFW's analysis of this incident is that 'blocking is done by blocking the specific port that the circumvention services listen on. When the user changes the blocked port to a non-blocked port and keep using the circumvention tools, the entire IP addresses may get blocked.' Interestingly, domain names used with these tools are not added to the Great Firewall's DNS or SNI blacklists, and blocking seems to be automatic and dynamic. 'Based on the information collected above, we suspect, without empirical measurement yet, that the blocking is possibly related to the TLS fingerprints of those circumvention tools,' the organization asserts. An alternative circumvention tool, naiveproxy, appears not to be impacted by these changes. 'It's not hard to guess why China might have chosen this moment to upgrade the Great Firewall: the 20th National Congress of the Chinese Communist Party kicks off next week,' notes the Register. 'The event is a five-yearly set piece at which Xi Jinping is set to be granted an unprecedented third five-year term as president of China.'

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