Packets in anonymous networks are fully protected. Therefore, traditional methods relying on packet header and higher layer information do not work to detect Distributed-Denial-of-Service (DDoS) attacks in anonymous networks. In this paper we propose to use observable statistics at routers that need no packet inspection to infer the presence of an attack. We propose packet resistance as a metric to detect the presence of attacks which reduce the availability of channel bandwidth for wireless routers in the core network. Our proposed detection framework is distributed, wherein each router in the network core monitors and reports its findings to an intermediate router. These intermediate routers form a hierarchical overlay to eventually reach a centralized attack monitoring center. The alarm messages are used to construct an attack path and determine the origin of the attack. We present simulation results to demonstrate the effectiveness of our proposed metric.