Who is DNS serving for? A human-software perspective of modeling DNS services

The Domain Name System (DNS) is indispensable for almost all Internet services. It has been extensively studied for applications such as anomaly detection. However, the fundamental question of whether a DNS query from a querent (i.e., an IP address) is triggered by humans or issued by software entities remains unclear. Addressing this question enables us to profile the querent's behavior from a human-software perspective, facilitating the understanding of “who is DNS serving for?”. In this study, we systematically performed querent-centric DNS modeling. Through in-depth measurements of three real-world DNS datasets of diverse origins, we developed an entropy-based method to distinguish between human and non-human queries and proposed a semi-supervised solution towards a community-level view for detecting and estimating software entities in a network. The solution can not only detect unknown software entities but is also NAT-compatible because it can detect and estimate software entities of multiple hosts NATed behind a single querent. An extensive evaluation demonstrates that our approach provides a new functionality for automatically disclosing the distinction between human and non-human domain names as well as a priori-independent and NAT-compatible functionality of discovering nearly 50% of the software entities and estimating their population using DNS queries.