Whois

What is Whois?

Whois is a publicly accessible protocol and database system that stores registration details about domain names, IP address blocks, and autonomous systems. It provides essential information about who owns a domain, when it was registered, which registrar manages it, and the associated contact details. Originally developed in the early days of the internet, Whois remains a foundational tool for network administration, cybersecurity investigations, and domain reputation analysis.

When someone queries a Whois record, they can see key metadata such as the registrant organization, registration and expiration dates, DNS name servers, and sometimes administrative or technical contact information. Although privacy regulations have restricted some data visibility in recent years, Whois continues to play a central role in identifying domain ownership and operational responsibility.

How Whois Works

Whois operates as a simple text-based query-response protocol, defined in RFC 3912. Each domain registrar maintains a database of registered domains and responds to Whois queries through a centralized lookup system.

Example Whois output for a domain:

Each registry, such as Verisign for .com domains or Nominet for .uk domains, manages the authoritative records for its top-level domains. When a Whois query is submitted, the system routes the request to the appropriate registry or registrar, which then returns the stored information for that domain.

Key Whois data fields include:

• Registrant and organization name
• Registrar and registration ID
• Creation, update, and expiration dates
• Name servers
• Contact email and administrative information (if available)

Uses of Whois Data

Whois data supports a variety of operational and security functions across the internet. It is frequently used by:

• Network administrators: To resolve domain ownership disputes or contact technical teams
• Security analysts: To investigate phishing campaigns or identify malicious domains
• Law enforcement: To trace cybercrime infrastructure or fraudulent websites
• Reputation systems: To assess domain age and legitimacy in spam filtering
• Brand protection teams: To monitor and take down spoofed or infringing domains

While Whois provides valuable transparency, privacy measures like GDPR have led to the redaction or anonymization of personal contact information in many regions. As a result, some registrars now provide limited access or redirect users to tiered disclosure systems where access depends on verification or legal justification.

Limitations and Modern Alternatives

Traditional Whois operates using a plain-text protocol without structured formatting, making automation and large-scale analysis challenging. To address this, a modern replacement known as RDAP (Registration Data Access Protocol) has been introduced. RDAP delivers Whois-style data in a standardized JSON format with secure HTTPS access, improving reliability and compliance with privacy laws.

Despite these changes, many legacy systems and lookup tools still rely on Whois for domain analysis, particularly when investigating DNS-based threats, ownership disputes, or infrastructure provenance.

Whois and DMARCeye

DMARCeye integrates Whois and RDAP data into its analytics engine to help organizations understand who is behind sending domains identified in DMARC aggregate reports. When unauthorized or suspicious sources appear, DMARCeye correlates authentication failures with Whois registration information to reveal whether those domains are legitimate partners, recently registered impersonations, or untrusted entities.

By connecting domain ownership intelligence with SPF, DKIM, and DMARC data, DMARCeye provides actionable insight into which domains require attention, allowing security teams to take proactive steps against abuse, spoofing, and domain-based attacks.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.