Researchers and network operators regularly monitor unused Internet address space called the darknet to understand malicious activities on the Internet such as malware infections, DDoS, and scanning to find vulnerable systems. The purpose of this study is to demonstrate the effectiveness of darknet monitoring across multiple organizations by conducting a detailed similarity analysis. In this paper, we analyze darknet data observed in two organizations in different industries and the first octet subnet range. We compared the results of the similarity analysis between intra-organization and inter-organization calculations by dividing the address space into multiple blocks so that one organization conducts similarity analysis in an intra-organization manner. The results show that the similarity of the source hosts is lower in the inter-organization calculation than in the intra-organization calculation. In addition, we monitor more source hosts in inter-organization. Moreover, this work also reports that the results differ depending on the destination ports/protocols. From the results obtained, we clarified the effectiveness of distributing the monitoring points of the darknet across multiple organizations.