Large-scale darknet monitoring is an effective approach to grasp a global trend of malicious activities on the Internet, such as the world-wide spread of malwares. There, however, have been a gap between the darknet monitoring and actual security operations on live networks, namely the global trend has less direct contribution to protect the live networks. Therefore, we propose a novel application of large-scale darknet monitoring that significantly contributes to the security of live networks. In contrast to the conventional method, wherein the packets received from the outside are observed, we employ a large-scale distributed darknet that consists of several organizations that mutually observe the malicious packets transmitted from the inside of the organizations. Based on this approach, we have developed an alert system called DAEDALUS (direct alert environment for darknet and livenet unified security). We present the primary experimental results obtained from the actual deployment of DAEDALUS.