AuthInfo

AUTHINFO is a command used in the Internet Whois protocol to provide authentication credentials to certain Whois servers. It was designed to allow access to restricted or authenticated data that anonymous queries could not retrieve, such as detailed contact information or registration data maintained by some registries. The exact implementation and syntax of AUTHINFO have varied across servers and over time, but a common pattern has been to send credentials in a two-step form, for example: AUTHINFO USER <username> followed by AUTHINFO PASS <password>. Some servers have supported alternative forms, such as a single combined command or different field names, depending on the registry’s software.

In practice, AUTHINFO is only effective on servers that support authenticated access; many modern Whois deployments do not require it and instead offer restricted data through other channels. Even when used, the protocol often transmits credentials in plaintext, making it vulnerable to interception on unencrypted connections. As a result, many registries have moved toward secure, web-based portals or newer protocols such as RDAP (Registration Data Access Protocol), which operate over HTTPS and provide structured, access-controlled data.

Overviewing its status, AUTHINFO remains a historical feature of the classic Whois ecosystem; it highlights the early attempt to balance public data availability with privacy and abuse prevention. Today, readers encountering AUTHINFO should expect limited support on contemporary servers and should prefer modern, secure access methods for registration data.

See also: Whois protocol, RDAP, ARIN, RIPE NCC, Whois databases.