From: Levenglick, Jeff (JLevenglick@fhlbatl.com)
Date: Sun Jul 08 2007 - 17:11:42 EDT
Zach,
Per standards, just about anybody can telnet to an smtp server on 25. (Do a dns lookup with MX set and telnet on 25 to the mail server)
Some people use the server as outbound only and change the listen port to something they know.
What they should do and it sounds like they did is restrict who is allowed to use the server to relay mail. (Relay-domain file ...ect)
If you have OS access just read that file and you can see who is allowed to relay.
Other security options include turning off commands link finger. (Sendmail option called goaway and a few other options)
The big rule is to turn off the deamon if the server is not going to be used.
-----Original Message-----
From: listbounce@securityfocus.com <listbounce@securityfocus.com>
To: pen-test@securityfocus.com <pen-test@securityfocus.com>
Sent: Sun Jul 08 00:58:57 2007
Subject: RE: TELNET and SMTP
Zach,
Just out of interest, you state that you weren't able to send an e-mail.
Were the source or destination addresses within your client's domain? Try
sending an "internal" email and see if you get the same response. If not,
then this can be used to send spoofed mail within the organisation.... e.g.
from HR to an employee supposedly firing them, or from the CEO to the cute
secretary in one of the departments harassing her sexually (the list goes
on).
-----Original Message-----
From: listbounce@securityfocus.com [mailto:listbounce@securityfocus.com] On
Behalf Of wymerzp@sbu.edu
Sent: 07 July 2007 22:31
To: pen-test@securityfocus.com
Subject: TELNET and SMTP
Hello all,
I'm looking at a client's site and they have unprotected access to port 25
(i.e. I can telnet to it and issue commands). When I attempt to send an
email I get this message '553 Relaying is not supported'. My question is
two-fold: 1)What could I do with the unprotected SMTP access if I can't send
mail. 2)What purpose do you believe that the SMTP service provides? Does the
SMTP simply recieve!?!? Thank you all, Zach
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