Whois Lookup

What is a Whois Lookup?

Whois is simply a plain text protocol that returns information from a database of Internet resources. It can reveal the owner or registered user of a resource; that may be a domain name, an IP address block or an autonomous system number (ASN).

Information returned includes physical addresses, email addresses of system staff, names and phone numbers. The DNS name servers of a domain are also displayed. Many domain registration services allow a private listing in which the details of the domain owner can be hidden, these became popular following the prevalence of spam being directed at domain owners.

The Whois protocol was based on the Finger protocol that goes back to 1977, during the very early days of the Internet (ARPANET). The Finger protocol allowed you to "finger" a remote host and the response from the plaintext protocol would reveal who was actually logged on to the system (and how long they had been logged on).

Whois is still a simple plaintext protocol that has a server component that listens on TCP port 43. Clients establish a connection to this port and transmit a text record with the domain or IP address that is to be queried against the Whois database. Since the protocol is so simple a telnet client can be used to query the whois service.