full-disclosure - Improving E-mail security...

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From: lsawyer at gci.com (Leif Sawyer)
Subject: Improving E-mail security...

Bengt Ruusunen writes:
> 
> Hello,
> 
> As everybody knows that recent viruses spread via sending 
> spoofed 'sender address'.
> 
> fex.
> 
> I am a person 'someone@...eone.com' and got so called 'return 
> mail' from 'someone@...eiving.organisation.com' telling that mail
> sent by me (which I never sent in a first place) cannot be delivered.
> Obviously containg somekind malware as an attachment.
>[...]
> - E-mail receiving server could check that 'very first original'
> From: line and if it is same than the receiver address ie.
> 'someone@...eone.com'
> 
> Perform an check to see if the 'sender identification' ie. 
> salted public key, GUID or something (X-Authenticated-Guid: 
> #0a845d299ca340087140) exists in mail header.
> 
> Delivery should be done only if an 'sender identification' 
> exist and the key matches.


What about mail MUA/servers which silently drop your optional
X-Authenticated-Guid: header?  You would be trashing every
mail from those clients.

Now if you used this in tandem with a spam filter software
like SpamAssassin, you could use it to re-weight the probability
of the response.
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