Censys is a platform that helps information security practitioners discover, monitor, and analyze devices that are accessible from the Internet. We regularly probe every public IP address and popular domain names, curate and enrich the resulting data, and make it intelligible through an interactive search engine and API.
Enterprises use Censys to understand their network attack surfaces. CERTs and security researchers use it to discover new threats and assess their global impact. Censys was founded by computer scientists at the University of Michigan, and data we collect has been used in hundreds of scientific papers by researchers around the world.
For more information, visit Censys.io.
One way that Censys finds publicly-reachable devices is by using Internet-wide scanning. We make a small number of harmless connection attempts to every IPv4 address worldwide each day. When we discover that a computer or device is configured to accept connections, we follow up by completing protocol handshakes to learn more about the running services.
We never attempt to bypass any technical barriers, exploit security problems, or otherwise access non-public-facing services, and we follow community best practices to reduce any burden on remote networks. The only data we receive is information that is publicly visible to anyone who connects to a particular address and port.
For technical information about the kinds of data Censys collects, visit our data definitions page.
Censys scans the Internet from the 126.96.36.199/23 subnet, which you can whitelist or blacklist if you wish.
We sometimes make follow-up connections from other machines at dynamic IP addresses, but blocking the addresses above is sufficient to prevent your device from appearing in our IPv4 dataset.
Censys data is sometimes used by researchers and network administrators to detect security problems and alert the operators of vulnerable systems. If you block our scans, you might not receive these important security notifications.
If you have questions about Censys scanning, please get in touch at firstname.lastname@example.org.