Re: E-Mail relay or break in?

[nathan () MMIND NET (Nathan Nichols)]

I believe that one of the Service Packs for Exchange 5.0 and Exchange 5.5
adds relay blocking (somebody correct me if I'm incorrect).  I'd go grab
SP2 for 5.5 and give it a shot.
-----
Nathan Nichols
Unix Systems Administrator
MasterMind Internet Services
918-743-6161

-----Original Message-----
From: Incidents Mailing List [mailto:INCIDENTS () SECURITYFOCUS COM]On
Behalf Of JJ Gray
Sent: Wednesday, February 09, 2000 5:40 AM
To: INCIDENTS () SECURITYFOCUS COM
Subject: Re: E-Mail relay or break in?

Strange... if I wanted to test that a mail server would allow open relay I
would make sure I could get the mail myself, to a dummy hotmail/yahoo
account... but your example is within a single domain.
AFAIK Exchange cannot be configured to prevent open relay, also the main
thing I noticed in the SMTP commands is the empty HELO command... RFC 821
says that this should identify the sender SMTP address to the receiver
SMTP.
Ideally the mail server should reject an empty HELO or at least complain
about it not being the source IP of the connection ( which should also be
logged ).   The rest of the SMTP commands are legit though.
It could just be a wind-up *shrug*   Bear in mind that spoofed email can
be
dangerous - if I spoof a mail from your CEO to you, asking sensitive
information, but have the reply-to address to hacker () example com ( which
you
don't see on most email clients ! ) then you will send me the info,
thinking
it will go to your CEO...
Digital signatures and/or encryption can help with this.

Regards,
            JJ

Sed quis custodiet ipsos custodes ?

----- Original Message -----
From: Seth Georgion <sysadmin () SASSPRODUCTIONS COM>
To: <INCIDENTS () SECURITYFOCUS COM>
Sent: Wednesday, February 09, 2000 2:56 AM
Subject: E-Mail relay or break in?
[snip]

> And here is the log of what the person typed in word for word.
>
>
> 2/8/00 3:14:42 PM : A connection was accepted from GATE.
> 2/8/00 3:14:42 PM : <<< IO: |HELO
> |
> 2/8/00 3:14:42 PM : <<< HELO
> 2/8/00 3:14:43 PM : >>> 250 OK
[snip]

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