nanog mailing list archives

Re: what happens when you put a typo in a DNSBL server?


From: Wes Hardaker <wjhns61 () hardakers net>
Date: Tue, 16 Jan 2007 13:19:40 -0800


"JL" == John Levine <johnl () iecc com> writes:

Previous to this date a misconfigured ISP was just not being
protected by the BL.  Now, it's potentially dropping all mail from
anyone because of the typo.

JL> If only.  I am constantly amazed at the bozos who misconfigure their
JL> DNSBL lookups and don't notice.

Part of the problem is that the protocol is designed to overlay an
existing protocol without providing a valid positive response.  In
this case, lame ISP configures a typo and goes for ages without
noticing that it didn't help them at all because every query was
getting a NXDOMAIN back and they didn't check the traffic.  Had this
been a real protocol you would have gotten back a 404 like message
instead!  Shoe-horning DNS (or any protocol) into a solution works
well only if you don't make mistakes.  And we know that never happens.

In the end, you don't get error messages when you misconfigure a
DNSBL.  That's an architectural issue with how DNSBLs work in the
first place.

-- 
"In the bathtub of history the truth is harder to hold than the soap,
 and much more difficult to find."  -- Terry Pratchett


Current thread: