vs. SecurActive Performance Vision. Reverse DNS (rDNS) is a method of resolving an IP address into a domain name, just as the domain name system (DNS) resolves domain names into associated IP addresses.One of the applications of reverse DNS is as a spam filter.s. SecurActive Performance Vision. Reverse DNS (rDNS) is a method of resolving an IP address into a domain name, just as the domain name system (DNS) resolves domain names into associated IP addresses.