full-disclosure - Swen Really Sucks

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From: jstewart at lurhq.com (Joe Stewart)
Subject: Swen Really Sucks

On Thursday 25 September 2003 12:27 pm, Schmehl, Paul L wrote:
> > The "From" or Return-Path address specified by the MAIL FROM:
> > transaction in the SMTP session is the real email address of the
> > infected user, or at least is what they entered on the fake
> > MAPI dialog
> > that Swen uses to get that information.
>
> Please tell me you don't believe this is true.  If you know anything
> about SMTP you know that the MAIL FROM: can be anything you want it
> to be.  And Swen certainly forges the sender, as the hundreds of
> bounces I get will testify.  There is *nothing* in an SMTP
> transaction that you can rely on except the headers *if* you know how
> to read headers.  If you don't, even those will fool you.

I am speaking from direct knowledge gained by reverse-engineering Swen. 
It is true that anyone can forge SMTP headers, but Swen does not forge 
the address in the MAIL FROM: transaction. It sends the email address 
provided to it by the infected user.

The bounces you are getting may be actual first-generation Swen 
messages, as a phony bounce message is one of the many formats it 
generates.

-Joe

-- 
Joe Stewart, GCIH 
Senior Security Researcher
LURHQ Corporation
http://www.lurhq.com/