Frequently Asked Questions
What ports and protocols does Censys scan?
For a complete list, see the 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, every known service in our entire dataset is evaluated for its age, and any service older than 24 hours is rescanned to verify its accuracy.
How complete is the Censys host data set?
Censys' next-gen scan engine scans 3,500 ports (with automatic service detection) and is also scanning from multiple perspectives to provide visibility of over 99% of the Internet.
Censys is also scanning the Internet at a high frequency, 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 the most 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 the same data as our highest-tiered customers: Censys datasets via Google BigQuery and up-to-date raw scan data for downloading. This access is strictly limited to non-commercial use. Learn more about research access.
Can I opt out of Censys scans?
Censys strives to be a good citizen of the security community. 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 they can be fixed. If you opt out of the research, you might not receive these important security notifications.
Censys never attempts to log in to any service, read any database, or otherwise gain authenticated access to any system. The only HTTP method Censys uses is GET; we do not POST data to any server.
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 any results from Censys data sets, but if you have blocked these subnets, your hosts will automatically be pruned out of our daily snapshots.
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, please reach out to our team at firstname.lastname@example.org.