The Great Firewall of China (GFC) represents one of the most sophisticated censoring infrastructures in the world. While several aspects of the GFC including HTTP keyword filtering and DNS tampering have been studied thoroughly in the past, recent work has shown that the GFC goes to great lengths to prevent its citizens from using the Tor anonymity network. By employing the so-called follow-up scanning technique, Tor bridge relays are blocked dynamically. In this thesis, we survey previous work in the area of the GFC ranging from HTTP keyword filtering and DNS tampering, to the Tor follow-up scanning. Furthermore, additional experiments are carried out to gain a better understanding of how the follow-up scanning is implemented as well as where the filtering occurs for different protocols.