ThreatSTOP provides sets of forward lookups where the NAME of the lookup is the reputation assigned to it. Unlike a traditional RBL, this lookup can be used directly in routing decisions. There is no messing around with reversing the quads, appending the zone, and then interpreting the number that comes back's measure of "badness". This seemingly simple idea is actually non-trivial to implement, due to limitations in the current nameservers. Also, it's only recently that firewalls have been powerful enough that having to compare connections to thousands of IP addresses wouldn't overwhelm their RAM and CPU.

Threatstop has filed a patent on this method, which is distinctly different from the current RBL method of disseminating IP reputation.