DNSBL is a Domain Name System-based Blackhole List, also known as «RBL» Real-time Blackhole List. It’s nothing more than a black (or white) list distributed via DNS protocol and it’s widely used by MTA, mail server, antispam, etc… in order to block spammers.

In this article I’ll show you how to create a DNSBL client and service from scratch, and how to protect your webapp thanks to http:bl by Project Honey Pot. Read the full article here: