[Esd-l] Spoofed email addresses

John D. Hardin jhardin at impsec.org
Fri Jun 14 07:12:01 PDT 2002

On Fri, 14 Jun 2002, Paul Ferwerda wrote:

> From looking at the headers it looks like the Return-Path was
> forged.  Is there any way to deal with this short of not
> notifying?

There's a limit to how smart the sanitizer can be made, and you can
only really catch forgery of invalid addresses. If a work running at
ferwerda.net forges the sender address as <paul at ferwerda.net>, how can
you (even manually) tell that's not valid?

> >> > From Culsart at azstarnet.com Thu Jun 13 17:38:58 2002 
> >> > Return-Path: <Culsart at azstarnet.com> 

> >> > Received: from Txkzxn (dhcp825.mc01.dsl.fastucson.net []) 
> >> > by cepheus.azstarnet.com (8.9.3/8.9.3) with SMTP id PAA14156 
> >> > for <webmaster at mxtabs.net>; Thu, 13 Jun 2002 15:38:45 -0700 (MST) 

This one is the original delivery. If there was some automated way to
query the ISP for which of their clients had at that
time, then we might be able to notify something close to the correct

Klez is a serious pain in the butt.

 John Hardin KA7OHZ    ICQ#15735746    http://www.impsec.org/~jhardin/
 jhardin at impsec.org                        pgpk -a jhardin at impsec.org
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