“WHOIS (pronounced as the phrase who is) is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system, but is also used for a wider range of other information. The protocol stores and delivers database content in a human-readable format.[1] The WHOIS protocol is documented in RFC 3912.”
http://who.is/whois-ip/ip-address/<IP Address>
http://who.is/whois/<Domain Name>
http://whois.domaintools.com/<IP Address>
http://whois.domaintools.com/<Domain Name>
http://www.t1shopper.com/tools/
http://www.all-nettools.com/toolbox/smart-whois.php
http://www.samdns.com/default.aspx
REFERENCE
A Firewall Engineer 