One of the most important, if not the most important servers to protect is your DNS server. Personnaly when people discuss how simple DNS lookups are and how any server can do it without giving the topic much thought it sends shivers along my spine. Your DNS server is equivelent to the nervous system of any network or server farm. By compromising your DNS server a hacker can redirect traffic to pretty much anywhere under guise of sending it to the proper server without clients ever knowing. It allows them to steal any and all data that you send to what users consider a secure connection. This is why Domain Name Servers should be the focal point for enhancing your security even before you start doing heavy analysis on the rest of your server applications.
This is general term describing a list of any type used to block individuals or groups. It can be a less technical list, a strictly formated digital list/database, or a proprietary formatted list. Broadly it refers to any list which is used to deny services, communication, information, or goods for a particular reason.
A Domain Name System based/block list (DNSBL) contains information about DNS zones. Information reguding IP Addresses exploitive and bad behavior (sending spam,viruses,etc.), and various DNS records is maintained. They vary in complexity sometimes containing TXT records for further information. Their sole purpose is to maintain a record of people's computers that apparently have a history of doing 'bad' things. It is easy to maintain this sort of blacklist, however your reliablity of who is doing bad things is very important, though making and distributing the list is usually simple. If you have a high level of statistical reliability, other network administrators may use your list if it is publically avalible. Almost all the lists carry disclaimers, are offered "as is", and are freely avalible. This Often grants them immunity against large corperations who threaten the maintainer of the list. Most of the time if you are not a repeat offender, and you ask nicely you can get a email address, ip, domain, etc. removed rom the lists. Some maintainers do automated testing regauding your application for removal to check to make sure your email server has basic security (such as releay turned OFF). There are many people and groups who maintain DNSBL's according to different standards, at varying qualities of service, sizes and statistical relability. Therefore you can be blacklisted by various sources, requiring you to contact serveral individuals to try and be removed from the list.
A Realtime Blackhole List (RBL) is an early type of blacklist designed by Paul Vixie (1997). It was one of the first type of popular digital blacklists that was widely distributed. This was later ran by a Mail Abuse Prevention System (MAPS). Like Xerox has the same generic meaning as a photocopy since they popularized the technology, RBL is often synonomous with the term DNSBL.
A Right-Hand Side Blacklist and Reverse Domain Name System based/block list (RDNSBL) are lists that are a DNSBL variant. RHSBL and RDNSBL use domain names of a reverse DNS resolution to IP addresses, instead of IP addresses to domain names (DNSBL).
There are many lists of black lists that contain information, and sometimes checking against multiple blacklists through automated services. As far as I know of this writing they are not required to be listed anywhere in a "Master List". Some good ones are:
