Reverse DNS lookup uses the Domain Name System (DNS) to find the domain name associated with an IP address. It can also reveal the owner’s contact information and is used to combat email spam. WHOIS maintains contact information for domain names and IP addresses.
To find the Internet domain name associated with a particular Internet Protocol (IP) address, you can use a procedure called reverse DNS lookup. This process uses a system called the Domain Name System (DNS) which links numerical computer addresses to domain names such as example.com. Further searches may reveal the name of the person or entity that registered a particular domain name, as well as contact information in some cases.
A person can use a reverse DNS lookup when they know the numerical IP address of a website and want to know the domain name associated with it. If so, you use an internet tool or website to type an IP address that is a series of numbers separated by periods, such as 123.456.123.456. As long as website designers have enabled the correct pointer records within the programming for the domain name at the server level, a submitted request for a particular IP address will return the correct information. This is the essence of a reverse DNS lookup, also called reverse DNS resolution (rDNS).
A reverse DNS lookup is also used to discourage email spam. Email users are often inundated with unwanted emails called spam. Some Internet mail servers use a technique called forward-confirmed reverse DNS lookup to weed out unsolicited messages from spammers who could be broadcasting an unwanted email to millions of people at once. This forward confirmed reverse DNS lookup means that a request is sent for a particular IP address, but it goes one step further as the result is then checked to make sure the relationship is valid.
Every computer that connects to the Internet does so through an Internet Protocol address. With the right hardware and software, this unique address can be traced back to a particular computer anywhere on the planet. However, numeric domain names can be hard to remember, so letters and numbers are used to route a domain name to its numeric IP address. The set of alphanumeric domain names is called the domain name system or DNS.
A separate database, called WHOIS, maintains contact information for administrative and technical contacts for domain names registered within the DNS. Additionally, WHOIS provides contact information for IP address block owners. A lookup similar to a reverse DNS lookup will reveal the person or entity that owns the domain name or IP addresses.
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