"On September 25, 2009, the Great Firewall of China blocked the public list of relays and directory authorities by simple IP address blocks. Currently, about 80% of the public relays are blocked by IP address and TCP port combination. Tor users are still connecting to the network through bridges. 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. If you want to help people in China get access to the uncensored Internet, run a bridge..."