[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: [suse-security] Email Spoofing



Eric,

It is possible to send multiple emails with one "connect / disconnect" session even to different recipients and from different "MAIL FROM" addresses.  Only the original connect and the final quit will be logged.  

Two ways to minimize the spoofing problem:

1.  Enforce reverse DNS lookups on the connecting IP address.
2.  RBL subscriptions, for what those are worth.

Another option (not necessarily recommended) is to force the "from" domain to match the reverse lookup completed on the connecting IP address.  This will break many email attempts from legitimate sources because the SMTP servers don't necessarily belong to the sending domain (MX gateway services, for instances).

Is that the question you are asking?

HTH,

Grant


-----Original Message-----
From: Eric Kahklen [mailto:eric@xxxxxxxxxxx] 
Sent: Wednesday, July 21, 2004 11:08 AM
To: suse-security@xxxxxxxx
Subject: [suse-security] Email Spoofing


We are using Suse 9.0 Professional.  I am getting email that is claiming 
to be from my domain and the Posfix logs confirm it is from an outside 
IP.  After searching the logs, I figured out where the connection 
initiated, and then the regular smtp traffic proceeded with the spoofed 
email address (user@xxxxxxxxxxxx) to my real users email address 
realusers@xxxxxxxxxxxx).  The unique identifiers helped me correspond 
the traffic.  There were two other email sessions that based on their 
unique identifier did not have the full smtp process.  For example, this 
is all that is entered in the logs for the unique process.  I usually 
see a connect and disconnect process before and after this and the 
random character user does not exisit!  BTW, this is a mail gateway for 
Exchange.

Any ideas??

Jul 20 11:54:59 gateway postfix/smtp[10247]: 649E6AD30: 
to=<user1@xxxxxxxxxxxx>, relay=10.0.0.5[10.0.0.5], delay=14, status=sent 
(250 2.6.0  <hxdgpusiesezuvbkmcc@xxxxxxxxxxxx> Queued mail for delivery)

Jul 20 11:55:10 gateway postfix/smtp[10247]: 8BFB2AD43: 
to=<user2@xxxxxxxxxxxx>, relay=10.0.0.5[10.0.0.5], delay=25, status=sent 
(250 2.6.0  <oityeuiuogzvyivawrs@xxxxxxxxxxxx> Queued mail for delivery)

Thanks,

Eric

-- 
______________________________________________________________________

Eric Kahklen, MS
530 4th Ave. W. 
Seattle, WA



-- 
Check the headers for your unsubscription address
For additional commands, e-mail: suse-security-help@xxxxxxxx
Security-related bug reports go to security@xxxxxxx, not here


This electronic message transmission is a PRIVATE communication which contains
information which may be confidential or privileged. The information is intended 
to be for the use of the individual or entity named above. If you are not the 
intended recipient, please be aware that any disclosure, copying, distribution 
or use of the contents of this information is prohibited. Please notify the
sender  of the delivery error by replying to this message, or notify us by
telephone (877-633-2436, ext. 0), and then delete it from your system.


--
Check the headers for your unsubscription address
For additional commands, e-mail: suse-security-help@xxxxxxxx
Security-related bug reports go to security@xxxxxxx, not here