Chinese authorities have tweaked the country's Internet censorship regime, known as the "Great Firewall," to block several popular virtual private network (VPN) services. The Guardian's Charles Arthur reports that China Unicom, one of China's largest Internet service providers, is now throttling connections upon use of a VPN .
VPNs are services that create quasi-tunnels within the Internet which can access otherwise blocked websites. Within China, VPNs allow millions of Internet users to access blocked services such as Twitter, Facebook, and the New York Times.
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