SMTP rejecting wrong HELO/EHLO domains will save the world (was: Backdoor in passworded ZIP not recognized by Kaspersky)

[Martin Mačok <martin.macok () underground cz>]

On Wed, Mar 03, 2004 at 11:36:09PM +0530, Aditya, ALD [Aditya Lalit Deshmukh] wrote:

> how about the smtp server simply rejecting mail from spoofed hosts
> ? as all the viruses generate spoofed hosts and it is very easy for
> any smtp server to do a dns lookup on the sending server, if the
> hostname / ip address do not match reject the message.

I guess you are talking about comparing HELO/EHLO domain with
reverse/forward DNS record for the IP of the host. (?)

Yes, this would definitely stop almost all SPAM/viruses instantly when
"turned on". It just have two little problems - it would also
definitely stop almost all email messages - and - there would be also
no problem for SPAM/viruses to use real domain in EHLO verb tommorow.

Martin Mačok

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