In the past, there was no way for users to find out what other domains, if any, a particular registrant owns without first translating a domain name into an IP address. But with the shortage of available IPv4 addresses, which resulted in the assignment of shared IP addresses to unrelated individuals or even companies, that approach has become riddled with difficulties.
Even if you can pinpoint the owner of an IP address, a shared one would provide users with a list of domains that may take a lot of time to sift through. If that IP address turns up as an indicator of compromise (IoC) in a publicly accessible report, affected users would have to go through each related domain’s WHOIS records to get to the bottom of the issue. Imagine how long that would take if you had 30 domains or more to scrutinize.
This post shows how users can find out who owns a domain name in five simple steps.