WHOIS is a TCP-based query/response protocol which is widely used for querying a database in order to determine the owner of a domain name, an IP address, or an autonomous system number on the Internet.

The WHOIS system originated as a method that system administrators could use to look up information to contact other IP address or domain name administrators (almost like a 'white pages').

Sectigo uses WHOIS databases to validate site information for the orders it receives.