The “Great Firewall of China,” designed to prevent citizens from accessing some overseas content, has apparently undergone an upgrade. Some observers say this may not only be an effort to stop citizens from reading or viewing Western information, but also to spy on international corporations doing business in the country who encrypt their internal communications. The Guardian report said VPN providers are now noticing it as well. Astrill, a VPN provider for users inside and outside China, has emailed its users to warn them that the Great Firewall system is blocking at least four of the common protocols used by VPNs.”]
Source: https://www.csoonline.com/article/2132698/could-china-blocking-vpns-lead-to-spying-on-business-.html