The DNS filtering apparatus of China's Great Firewall (GFW) has evolved considerably over
the past two decades. However, most prior studies of China's DNS filtering were performed
over short time periods, leading to unnoticed changes in the GFW's behavior. In this study,
we introduce GFWatch, a large-scale, longitudinal measurement platform capable of testing
hundreds of millions of domains daily, enabling continuous monitoring of the GFW's DNS
filtering behavior. We present the results of running GFWatch over a nine-month period …