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Forging Return-Path (was: Re: Vintage Charlie....)

2002-05-16 20:23:55
On Thu, 2002-05-16 at 13:37, Philip Guenther wrote:
Paul Thomas <cueman(_at_)cuenet(_dot_)com> writes:
Heh, Charlie seems to be hitting his stride today. Have  another
cup of coffee Charlie!;)

You might now like how he says it, but did you pay attention to the
_content_?  He is correct: sending a bounce message to the header
sender is a Bad Thing.  Use "formail -r", "formail -rt" when generating
bounces.

The sanitizer does this, and always has. 

I've been checking the Klez bounces from my domain and I'm seeing 80% to
90% correlation between Return-Path: and the domains in the Received:
headers.

Some comments and questions:

(1) I haven't seen the headers on the messages claiming to be from Mr.
Summers so I don't know if the attack message contained a Return-Path:
header. I have seen a few messages (not necessarily from Klez) that do
not. I've asked Paul if he still has the administrator notifications
from those messages so I can see them.

(2) Is it possible to forge a Return-Path: header? Or do the MTAs
override this one?

(3) If it is possible to forge the Return-Path: header, does anyone know
whether any Klez variants do so?

-- 
 John Hardin KA7OHZ    ICQ#15735746    http://www.impsec.org/~jhardin/
 jhardin(_at_)impsec(_dot_)org                        pgpk -a 
jhardin(_at_)impsec(_dot_)org
  768: 0x41EA94F5 - A3 0C 5B C2 EF 0D 2C E5  E9 BF C8 33 A7 A9 CE 76 
 1024: 0xB8732E79 - 2D8C 34F4 6411 F507 136C  AF76 D822 E6E6 B873 2E79
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