Censys: A Map of Internet Hosts and Services

In 2015, we released Censys to lower the barrier to entry for researchers to study Internet devices by continually collecting and packaging Internet scan data. Since then, as we have learned more about how best to capture the complex behavior of Internet services and begun to serve commercial and government users, we have re-architected every aspect of how Censys operates. Motivated by requests from the community, we present Censys' evolution and current architecture, evaluate its visibility, and detail how Censys has been used by research, industry, and government. Finally, informed by our operational experiences, we discuss unsolved problems and the lessons we have learned. We hope that our work provides the transparency needed for researchers to soundly use Censys data and offers directions for future research.