Frequently Asked Questions
What ports and protocols does Censys scan?
For a list of all 107 protocols and 3500+ ports, see the Censys Scanning Overview.
How frequently does Censys scan the Internet?
Censys is continuously scanning the Internet to find new services, remove old services, and refresh data about current services in its free searchable index.
Discovery scans are performed 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 host 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 scan provides visibility of over 99% of the public Internet by scanning the most ports (3,500+) using automatic service detection from multiple scanning perspectives.
The Censys datasets also have higher fidelity in terms of tracking changes to the Internet over time and providing the most accurate snapshot of the current Internet.
What third-party sources does Censys use to enrich Search data?
We provide geolocation data using the Maxmind GeoIP2 City Lite dataset and routing information using the RouteViews dataset.
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 available in 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.
How does Censys Search quota consumption work?
Every call to the Censys Search and Data API endpoints, including use through the UI and paging through results, consumes monthly quota. The only exception is viewing a host summary page in the web UI.
Can I opt out of Censys scans?
Censys strives to be a good citizen of the security community. Our scans help the scientific community accurately study the Internet and help security practitioners defend it.
Censys scans only obtain information: Censys never attempts to log into any service, read any database, or otherwise gain authenticated access to any system.
If you wish to opt out, you can configure your firewall to drop traffic from the subnets we use for scanning. Find them here.
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 support@censys.io.
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