Port 43WHOIS
WHOIS is a query and response protocol commonly used for querying databases of Internet resources such as domain names and IP address registrations. Often used by network administrators, cybersecurity professionals, and domain registrars, it provides useful information about domain ownership, status, and contacts. Originally developed as a simple and open service, it still plays a vital role in Internet governance and investigations..
- transport
- tcp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 6,628
single transport
payload readable on path
registered with iana
caution
rank 771 of 993 · top 78%
Technical Details
what runs on :43The WHOIS protocol operates primarily over TCP port 43 and facilitates the retrieval of registration information related to domain names, IP addresses, and autonomous system numbers from digital registries. A client sends a text-based query string containing a domain name or IP address, and the WHOIS server responds with a plain-text record containing details such as registrant organization, contact information, registration dates, and name server data.
Designed in the early days of the ARPANET, WHOIS is defined in a set of RFCs including RFC 3912, which describes its simple query-response model over TCP. Because WHOIS uses a line-oriented plain text format, implementations and responses vary somewhat between registries, leading to inconsistencies that can complicate automated parsing and data aggregation.
Despite the emergence of alternative systems like RDAP (Registration Data Access Protocol), WHOIS remains widely employed. It has a straightforward architecture: minimal session setup, no encryption by default, and lacks structured data formats — characteristics that make it easy to use but limit its extensibility and security.
Security Information
exposure of :43risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
web services averages 3.9 across 112 ports — this one sits 0.1 above.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp
every listening transport is another surface to filter at the edge
security overview
Common vulnerabilities related to the WHOIS protocol stem from its unencrypted nature and information disclosure risks:
- Data Harvesting & Privacy: Since WHOIS responses include registrant details and contact information in plain text, malicious actors can scrape this data for spam campaigns, social engineering, or targeted attacks.
- Lack of Encryption: Because WHOIS operates without transport encryption, queries and responses can be intercepted and monitored by adversaries on the network.
- Reflection or Abuse: Open WHOIS servers can be abused to amplify reconnaissance or used in denial-of-service preludes by attackers gathering infrastructure intel.
Mitigations include:
- Data Redaction: Registries increasingly redact sensitive data or require logged-in access for detailed records, complying with privacy regulations like GDPR.
- Migration to RDAP: Transitioning to RDAP improves access control, data security, and structured responses.
- Network Protections: Limit access to internal WHOIS services, monitor traffic patterns, and implement rate limiting to reduce data scraping.
- Encryption Tunnels: When confidentiality is critical, using VPNs or encrypted proxies around WHOIS queries can protect data in transit.
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risk mix of the 8 listed
- safe13%
- caution88%
0 of 8 encrypted