[Dshield] Denying incoming email by reverse lookup of ISP DHCP-edaddresses

Stef stefmit at gmail.com
Fri Jun 17 18:58:18 GMT 2005


On 6/17/05, Brian Dessent <brian at dessent.net> wrote:
> Stef wrote:
> 
> > so my question is: does anyone know of a "canned" script, or add-on to
> > std email servers (sendmail, postfix, etc.), or a standalone third
> > party solution, with all the potential format of name-addresses like
> > the above, pre-built - before I start writing my own (perhaps going
> > after the email header's IP, and doing a reverse lookup of the
> > original IP, and rejecting the ones where the IP x.y.z.w resoved to a
> > name containing x-w-z-w ... but I am not sure if this is the rule for
> > all ISPs)?!?
> 
> Every decent MTA on the planet has the capability to consult DNS
> blocklists, and so configure it just consult one of the "dynamic IP
> address range" DNSBLs such as dul.dnsbl.sorbs.net.
> 
> Brian

What the h*** was I thinking - instead of imagining tons of scripting
scenarios, I should have thought of a solution like this - especially
as I used to contribute to such with my email honeypots. Duh ...

... thank you, Brian, and all the others who suggested this. I will
check this right away. I guess the "problem" is closed.

Stef




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