The Chinese authorities have tightened internet censorship ahead of Thursday's 60th anniversary of communist rule, according to reports.
The Tor project — a network of virtual private tunnels that is often used for anonymous communication and web surfing — said in a blog post on Sunday that the Great Firewall of China, which is operated by the Ministry of Public Security, had been blocking Tor relays since 25 September. These relays are used by the web surfer's Tor client in order to build a circuit of encrypted connections through relays on the network.
In the blog post, Tor project member 'Phobos' said the Chinese government had succeeded in blocking 80 percent of Tor public relays within the country, using IP address and TCP port blocks. However, Phobos said, Tor users were circumventing these blocks by using bridges — Tor relays that are not listed in a public directory of relays.
"Tor users are still connecting to the network through bridges," wrote Phobos. "At the simplest level, bridges are non-public relays that don't exit traffic, but instead send it on to the rest of the Tor network."
Meanwhile, the Chinese government has also stepped up efforts to prevent the use of virtual private networks (VPNs) and censorship circumvention software such as Freegate, according to the civil liberties and press freedom organisation Reporters without Borders (RWB).
"What the authorities are trying to portray as a big celebration is turning into a major headache for internet users," RWB said in a statement on Tuesday.
The organisation said "government security paranoia" had led to the clampdown. Three Mongol websites have been "rendered inaccessible in the past three weeks", said RWB, while sites using the Uyghur language remain blocked after unrest in the Xinjiang province in July.
In a separate statement on 18 September, RWB said it was "very worried" about reports of a more powerful version of the Green Dam censorship software, called Landun (Blue Shield or Dam), which internet service providers in Guangdong province had been ordered to install.
"It was encouraging that the government backed down on Green Dam in the face of a public outcry in China and abroad, and protests from internet players. But the reports of Blue Shield's installation by some ISPs sound frightening for the protection of personal data and online free expression in China," RWB said.
Blue Dam is intended to provide stronger protection against adult sites than that supplied by Green Dam, and to increase the government's internet monitoring and filtering capabilities, according to RWB.
In addition, more proxies had become inaccessible, RWB said. Proxies allow users to sidestep firewall restrictions.