RE: Relaying Problem question - still fighting it!
- From: "Allen, Chris" <CAllen@xxxxxxxxxxxxxxxx>
- To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
- Date: Tue, 30 Sep 2003 14:19:37 -0400
I was in the exact same boat. This is what we did to resolve it:
In Exchange System Manager ->Administrative Groups->site
name->Servers->server name->Protocols->SMTP->Default Smtp Virtual Server
properties, select the Access tab, then click the relay button. In the
Relay Restrictions window, we allowed "All except the list below" and
added the firewall's internal IP as our firewall NATs all traffic
including SMTP making all inbound email to appear to be coming from the
firewall IP. What this does for us is lets our internal users relay
since we have some apps that must be able to, but at the same time,
stops all outbound traffic from relaying. This may differ for you.
Chances are, you will need to select "Only the list below" and put in
your internal network range.
Now, the important part, Uncheck the "Allow all computers which
successfully authenticate to relay, regardless of the list above." What
this will do is confine relaying to the internal IPs, No longer will an
external user be able to relay using an authenticated user's
information.
We were having issues with a spam gang out of the Chongqing province of
china. They brute force attacked our network in an attempt to find valid
user-name/passwords and then, when found, started relaying through us
regardless of our IP restrictions. Unchecking the box put a stop to
that. It is still a good idea to reset passwords though as you really
don't know which accounts have been compromised. Yeah its an
inconvenience, but not as much as some malicious entity using your
network to wreak havoc.
Is the spam all originating from bluestellnn@xxxxxxxxxx where domain.com
is some random, yet valid domain (ie yahoo.com) and the nn is an
enumeration? If so, it is the same gang and you might want to add their
ip range to a deny rule in your firewall. It is as follows:
211.158.32.0/20
211.158.48.0/21
211.158.80.0/20
219.153.144.0/20
After doing these steps, the spam has disappeared from my queues.
If this works for you, we might want to see if we can get Microsoft to
document this in their knowledge base.
Chris Allen
Systems Administrator
Metron North America
-----Original Message-----
From: KEN MORRIS [mailto:KMORRIS@xxxxxxx]
Sent: Tuesday, September 30, 2003 1:32 PM
To: [ExchangeList]
Subject: [exchangelist] Relaying Problem question - still fighting it!
http://www.MSExchange.org/
Hi,
Our server has been compromised by an outside session using an internal
name/password, and our E2K server queues keep on filling up. I have had
up to 400 queues created over night and some of the queues can have well
over 600 messages each waiting to be sent (I have frozen most of my
queues as a precaution). These relays are being set up after we are
closed.
I am curious to see if anyone can answer the question of who would have
the rights to create a remote session to relay? Does it have to be an
admin account or can it be a standard user?
I have eliminated the Fire Wall by placing it on the restrictions for
the SMTP. and have unchecked the allow all to relay. So I am stumped as
to how they are still being able to set up the relaying. My next plan is
a forced network wide password change, after that...... I have to come
up with a "Plan C".
I am having the problem of trying to convince the powers that be, that
all user accounts need to have their passwords changed in order to
eliminate this hack. I am also recommending that our Domain Admin
accounts be made into guest accounts and new Domain Admin accounts be
created. Does anyone have any other suggestions and or reading that I
could do. So far I have found very little on this type of attack.
Thanks for your help!
Ken
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