Frequently Asked Questions
What ports and protocols does Censys scan?
For a complete list, see Censys Scanning Overview.
How frequently does Censys scan the Internet?
We perform discovery scans on several schedules based on the popularity of certain ports and networks (such as those allocated to cloud providers) in the IPv4 address space. Every day, known services in the entire dataset are evaluated for their age, and any service older than 24 hours is refreshed.
How does Censys find more hosts than Shodan?
Censys' next-gen scan engine scans more ports (with automatic service detection), and is also scanning from multiple perspectives to provide customers visibility of over 99% of the Internet. Censys is also scanning the Internet at a higher frequency than Shodan, resulting in a dataset with higher fidelity, both in terms of being able to track changes to the Internet over time, as well as providing an accurate snapshot of the current Internet.
What third-party sources does Censys use to enrich Search data?
What access does Censys provide for researchers?
We provide academic and other non-commercial researchers with free access to Censys datasets on Google BigQuery as well as up-to-date raw scan data. This access is strictly limited to non-commercial use. Learn more about research access.
Can I opt out of Censys scans?
Censys scans help the scientific community accurately study the Internet. The data is sometimes used to detect security problems and to inform operators of vulnerable systems so that they can fixed. If you opt-out of the research, you might not receive these important security notifications.
However, if you wish to opt-out, you can configure your firewall to drop traffic from the subnets we use for scanning:
Additionally, our HTTP-based scans use a Censys specific user-agent, which can be used to filter requests from our scanners.
Mozilla/5.0 (compatible; CensysInspect/1.1; +https://about.censys.io/)
We do not remove results from Censys, but if you have blocked these subnets, the results will automatically be pruned out.
What is Censys' relationship with the University of Michigan and Google?
Censys originally started as an academic research project at the University of Michigan. From 2015–2017, Censys was operated at Michigan with generous support from the Google Anti-Abuse Team. During this time, our license restricted access to non-commercial research. Since then, we've spun out from the University of Michigan into an independent company.
What is Censys' relationship with the ZMap Project?
Censys was started by the same team that created ZMap, and the Censys legacy scanner used many of the ZMap tools to collect and annotate data. The ZMap Project is and will remain an independent open-source project, and is primarily maintained by the Censys development team.
We are staunch supporters of open-source software.
What if I have a different question?
If you didn't find an answer to your question, feel free to reach to our team at firstname.lastname@example.org.