RBL - Revision history

Jimbo at 21:19, 21 June 2007

2007-06-21T21:19:18Z

Jimbo at 18:05, 5 May 2007

2007-05-05T18:05:20Z

Ice: reverted to 21:04, 21 May 2006

2007-04-12T18:26:25Z

reverted to 21:04, 21 May 2006

200.238.102.170 at 16:35, 10 April 2007

2007-04-10T16:35:32Z

Jimbo at 21:04, 21 May 2006

2006-05-21T21:04:09Z

New page

'''RBL''' is an acronym for '''R'''eal-time '''B'''lack-hole '''L'''ist - a list of IP addresses and/or URLs that nobody wants anything to do with, updated constantly in (you guessed it) real time. RBL's are most frequently used to filter out various types of spam, including the "traditional" email variety as well as the newer but increasingly more problematic [[comment spam]].

A typical RBL server is a very simple purpose-oriented [[DNS]] server which returns "no answer" if the IP being fed to it isn't on its list, and returns a special answer - usually 127.0.0.2 - if the IP is found. In order to check against the RBL, the IP is deconstructed and put together backwards in front of the RBL server's domain name - for example, in order to check the IP address 1.2.3.4 against the fictitious RBL server rbl.spammersarebad.net, you would try to resolve the URL 4.3.2.1.rbl.spammersarebad.net.

server# '''dig +short A 4.3.2.1.rbl.spammersarebad.net'''
127.0.0.2

Aha - the RBL returned 127.0.0.2, so it looks like the IP address 1.2.3.4 is on their list. Most RBLs will give you a little information about what's on their list, if you query them for a TXT record. Usually, the TXT record gives you an URL for a webpage which will tell you more about the list, whether or not the IP is still listed, and possibly (but possibly not) something about why it's listed or for how long it is scheduled to remain listed.

server# '''dig +short TXT 4.3.2.1.rbl.spammersarebad.net'''
"Blocked - see <nowiki>http://rbl.spammersarebad.net/bl.shtml?1.2.3.4</nowiki>"

By comparison, if we ask about an address that isn't on the list, we get no answer at all for either A or TXT records:
server# '''dig +short A 5.4.3.2.rbl.spammersarebad.net'''
server# '''dig +short TXT 5.4.3.2.rbl.spammersarebad.net'''
server#

See also [[Mail toaster]], a freebsdwiki.net special configuration of [[Qmail]] and several other mail applications which includes built-in RBL filtering.

[[Category:FreeBSD Terminology]]

← Older revision		Revision as of 21:19, 21 June 2007
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	See also [[Mail toaster]], a freebsdwiki.net special configuration of [[Qmail]] and several other mail applications which includes built-in RBL filtering.		See also [[Mail toaster]], a freebsdwiki.net special configuration of [[Qmail]] and several other mail applications which includes built-in RBL filtering.

−	[[Category:FreeBSD Terminology]]	+	[[Category:FreeBSD Terminology]][[Category:DNS]]

@@ Line 3: / Line 3: @@
 A typical RBL server is a very simple purpose-oriented [[DNS]] server which returns "no answer" if the IP being fed to it isn't on its list, and returns a special answer - usually 127.0.0.2 - if the IP is found.  In order to check against the RBL, the IP is deconstructed and put together backwards in front of the RBL server's domain name - for example, in order to check the IP address 1.2.3.4 against the fictitious RBL server rbl.spammersarebad.net, you would try to resolve the URL 4.3.2.1.rbl.spammersarebad.net.
-  server# '''dig  short A 4.3.2.1.rbl.spammersarebad.net'''
+  server# '''dig +short A 4.3.2.1.rbl.spammersarebad.net'''
 .0.0.2
 Aha - the RBL returned 127.0.0.2, so it looks like the IP address 1.2.3.4 is on their list.  Most RBLs will give you a little information about what's on their list, if you query them for a TXT record.  Usually, the TXT record gives you an URL for a webpage which will tell you more about the list, whether or not the IP is still listed, and possibly (but possibly not) something about why it's listed or for how long it is scheduled to remain listed.
-  server# '''dig  short TXT 4.3.2.1.rbl.spammersarebad.net'''
+  server# '''dig +short TXT 4.3.2.1.rbl.spammersarebad.net'''
   "Blocked - see <nowiki>http://rbl.spammersarebad.net/bl.shtml?1.2.3.4</nowiki>"
 By comparison, if we ask about an address that isn't on the list, we get no answer at all for either A or TXT records:
-  server# '''dig  short A 5.4.3.2.rbl.spammersarebad.net'''
+  server# '''dig +short A 5.4.3.2.rbl.spammersarebad.net'''
-  server# '''dig  short TXT 5.4.3.2.rbl.spammersarebad.net'''
+  server# '''dig +short TXT 5.4.3.2.rbl.spammersarebad.net'''
   server#