Whois lookup

Perform an Online Whois Lookup of a domain or IP address to find the registered owner, netblock, ASN and registration dates.

About the Online Whois Lookup

An Online Whois Lookup is an easy and fast way to find the ISP, Hosting provider and contact details for a domain or IP address. There are many uses for Whois data that can be utilised by attackers and defenders in the information security sector.

By having access to whois lookup online it is possible to gather the required information without having a whois client installed on your system. If you are running a Linux or *nix based system installation of a whois client is generally a simple matter.

Useful for tracking down attackers when defending or finding targets to attack when on the offensive. A whois lookup can reveal organisational details, IP ranges to scan and the email addresses of technical staff. This information is commonly found in the information gathering phase of an assessment or planned attack.

This Online Whois Lookup Tool simply runs the whois command line tool that is packaged in most Linux operating systems. With the results displayed in your web browser.

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.

Using Telnet to perform a Whois Lookup

With whois being a simple plain text protocol it is possible to use a standard telnet (or netcat) client to access whois data.

test@testserver:~$ telnet whois.iana.org 43
Connected to ianawhois.vip.icann.org.
Escape character is '^]'.
% IANA WHOIS server
% for more information on IANA, visit http://www.iana.org
% This query returned 1 object

refer:        whois.verisign-grs.com

domain:       COM

organisation: VeriSign Global Registry Services
address:      12061 Bluemont Way
address:      Reston Virginia 20190
address:      United States

contact:      administrative
name:         Registry Customer Service
organisation: VeriSign Global Registry Services
address:      12061 Bluemont Way
address:      Reston Virginia 20190
address:      United States
phone:        +1 703 925-6999
fax-no:       +1 703 948 3978
e-mail:       info@verisign-grs.com

contact:      technical
name:         Registry Customer Service
organisation: VeriSign Global Registry Services
address:      12061 Bluemont Way
address:      Reston Virginia 20190
address:      United States
phone:        +1 703 925-6999
fax-no:       +1 703 948 3978
e-mail:       info@verisign-grs.com

nserver:      A.GTLD-SERVERS.NET 2001:503:a83e:0:0:0:2:30
nserver:      B.GTLD-SERVERS.NET 2001:503:231d:0:0:0:2:30
nserver:      C.GTLD-SERVERS.NET 2001:503:83eb:0:0:0:0:30
nserver:      D.GTLD-SERVERS.NET 2001:500:856e:0:0:0:0:30
nserver:      E.GTLD-SERVERS.NET 2001:502:1ca1:0:0:0:0:30
nserver:      F.GTLD-SERVERS.NET 2001:503:d414:0:0:0:0:30
nserver:      G.GTLD-SERVERS.NET 2001:503:eea3:0:0:0:0:30
nserver:      H.GTLD-SERVERS.NET 2001:502:8cc:0:0:0:0:30
nserver:      I.GTLD-SERVERS.NET 2001:503:39c1:0:0:0:0:30
nserver:      J.GTLD-SERVERS.NET 2001:502:7094:0:0:0:0:30
nserver:      K.GTLD-SERVERS.NET 2001:503:d2d:0:0:0:0:30
nserver:      L.GTLD-SERVERS.NET 2001:500:d937:0:0:0:0:30
nserver:      M.GTLD-SERVERS.NET 2001:501:b1f9:0:0:0:0:30
ds-rdata:     30909 8 2 E2D3C916F6DEEAC73294E8268FB5885044A833FC5459588F4A9184CFC41A5766

whois:        whois.verisign-grs.com

status:       ACTIVE
remarks:      Registration information: http://www.verisigninc.com

created:      1985-01-01
changed:      2017-06-22
source:       IANA

Connection closed by foreign host.

We can see that by simply entering the domain we were able to get a response from the iana.org whois server. The important information contained in this response is a pointer to the whois server we need to talk to get more information about our domain.

The pointer is this snippet whois: whois.verisign-grs.com

Lets try again using the verisign-grs.com whois server.

test@testserver~:$ telnet whois.verisign-grs.com 43
Connected to whois.verisign-grs.com.
Escape character is '^]'.
   Registry Domain ID: 1064667694_DOMAIN_COM-VRSN
   Registrar WHOIS Server: whois.enom.com
   Registrar URL: http://www.enom.com
   Updated Date: 2017-04-25T02:32:05Z
   Creation Date: 2007-07-04T01:13:38Z
   Registry Expiry Date: 2020-07-04T01:13:38Z
   Registrar: eNom, Inc.
   Registrar IANA ID: 48
   Registrar Abuse Contact Email:
   Registrar Abuse Contact Phone:
   Domain Status: clientTransferProhibited https://icann.org/epp#clientTransferProhibited
   DNSSEC: unsigned
   URL of the ICANN Whois Inaccuracy Complaint Form: https://www.icann.org/wicf/

Now we have more information, including the DNS servers for the domain, the creation date and the registry expiry date.

Use Cases for a Whois Lookup

Incident Response and Threat Intelligence

The most obvious benefits of a whois lookup for those responding to a security incident is identifying the netblock and ISP that owns a particular IP address. From this information the incident responder can contact the owner of the netblock in order to alert the provider to the presence of malicious traffic.

Historical Whois records are also available that allow a responder to search for details in the whois data that may be present across multiple investigations or targets. For example you can search whois data to find an email address across multiple domains and determine when the email address first appeared in a whois record.

Troubleshooting Network Issues with Whois

With access to the whois data a network engineer investigating a path across the Internet may notice a particular network is introducing significant latency. Using an online whois lookup the network engineer will be able to determine the owner of the network in question and contact the engineers responsible for that network.

Whois Lookup API

Another way to query the whois service is to use the API. The HTTP response from the API will be returned in a simple text based format.


The API is designed to be used in an ad-hoc fashion not for bulk queries and is like all our IP Tools is limited to 100 (total) requests from a single IP Address per day.

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