A wireless network is more vulnerable to denial of service (DoS) attacks than a wired one. In this paper we propose a new DoS defense scheme toward actively resisting DoS attacks. A mobile terminal generates an authorized anonymous ID (AAI) using its true ID, and assigns its true ID with the produced AAI. Using an AAI, a legitimate mobile terminal will be authenticated by the wireless network, however, its true ID is concealed, and it ‘disappears’ to potential attackers. This method can be used to defend several kinds of DoS attacks at the same time. Additionally it can also be used to alleviate other kinds of security threats in wireless networks, such as eavesdropping. We demonstrate our proposed method in detail in a new application network: UMTS-WLAN (Universal Mobile Telecommunication Systems - Wireless Local Area Network) network, and provide some simulation results in OPNET 10.0 A environment.