DNSbl
The name DNSbl stands for DNS blocking list. Here the word "DNS" itself stands for Domain Name System.
So what is DNS to begin with? Every computer connected to the internet has an
IP address associated with it. This
IP address looks something like 64.233.187.99 . But since it is tough remember these numbers, each machine's
IP address is usually given a name which can be remembered. For example, the above
IP address 64.233.187.99 is associated with
www.google.com∞. If you want to know the
IP address that your machine is using currently, go to
www.whatismyip.com∞. The DNS essentially translates the name of the machine (in this case www.google.com) to the
IP address (in this case 64.233.187.99). A server which provides this service is called "DNS server". More information on DNS can be found at
Wikipedia:Domain_Name_System∞.
A DNSbl is simply a list of
IP addresses which satisfy a particular criterion. SpamCop's DNSBL is called
SCBL (spamcop blocking list). There are many other DNSbl's out there besides
SCBL. Depending the criterion used to build these DNSbls, they can be used for various purposes. For example, the
SCBL can be used by mail servers, network servers to identify potential spam email. There are DNSbls which can be used to identify trusted
IP addresses, specific
ISP's, countries etc.,
The following is not exactly related to DNSbl but is related to
SCBL . Please consider deleting this...
The
SpamCop.net DNSbl lists
IP addresses that
spam has been reported to originate from. It is aggressive, and may list real mail servers.
Some list only
IP addresses that have been shown to be compromised and abused by spammers. Others list
IP addresses that are known to be controlled by spammers.
These are known as conservative DNSbls.
And some list
IP addresses that are
DHCP∞ assigned. These are known as Dyanmic list and sometimes DIALUP lists. Many mail servers will not accept e-mail from these addresses.
Use of conservative DNSbls can block over 80% of the incoming
spam usually with out any real e-mail being rejected unless the sender's mail server has a severe security problem. Adding a good
DHCP∞ blocking list to that can eliminate most of the remaining spam with a very small chance of rejecting a real e-mail.
An aggressive DNSbl can be used to indicate if additional tests should be done on an incoming e-mail to see if it is
spam or real e-mail.
Also see
rDNS
CategorySpamCopGlossaryWikiD
CategoryPagesUnderConstruction
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