Question

How do I identify machines generating spam on my network

Asked by: tmutsambwa

Our domain IP has been black listed as a spam source. I am trying to find out the machine on my network generating the spam. My setup is as follows:

I have an exchange server 2007 running on Windows server 2008. My public IP address is on a cisco 1751 router. All clients on the network use the cisco router as a gateway. I have done nat to make traffic on port 25 to go to the mail server on port 25.

I have defined access lists:
access-list 110 permit tcp host 192.168.0.222 any eq smtp
access-list 110 deny   tcp any any eq smtp
access-list 110 permit ip any any

Despite this my IP got listed. I would like to know which machines are causing me the problem.

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Asked On
2009-09-04 at 10:59:40ID24708450
Tags

spam

,

exchange 2007

,

windows server 2008 cisco 1751 router

Topic

Exchange Email Server

Participating Experts
6
Points
500
Comments
12

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Answers

 

by: Gunter17Posted on 2009-09-04 at 11:03:32ID: 25261951

Is your server an open-relay?

http://technet.microsoft.com/en-us/kb/kb00324958.aspx

Otherwise, you will need to look at your outbound queue and hope the sender address wasnt spoofed.

 

by: GraemeEvans1Posted on 2009-09-04 at 11:07:26ID: 25261971

assuming the rules on your router are working only 192.168.0.222 can be sending spam

test the rules are working by using telnet on a computer that shouldn't be able to send mail

eg
telnet smtp1.google.com 25

you should see no text

unless your server is being used to send it, on the exchange server check the queues don't have hundreds / thousands of erronious messages, and check in message tracking what has been sent (look in tools in exchange console)

Also run an open relay test such as http://www.abuse.net/relay.html

 

by: MesthaPosted on 2009-09-04 at 11:57:29ID: 25262340

Its really hard to turn Exchange 2007 in to an open relay.
Are you sending email out directly or via a smart host? If you are sending it directly then look at the queues. If they are clean then it isn't the server sending the messages.

Have you tested whether a client can connect to a remote server on port 25?

Simon.

 

by: alanhardistyPosted on 2009-09-04 at 12:00:53ID: 25262366

 

by: ikalmarPosted on 2009-09-04 at 12:16:50ID: 25262515

 

by: northernwindPosted on 2009-09-04 at 12:51:36ID: 25262805

have you analyzed your mail queues? are messages building up? do you receive a lot of messages from postmaster@yourdomain.com?

 

by: ikalmarPosted on 2009-09-04 at 12:56:13ID: 25262835

sorry for my other conmments.,.. this for other topic.....

please try it find who use this smtp port:

access-list 110 deny   tcp any any eq smtp log

 

by: alanhardistyPosted on 2009-11-07 at 08:57:16ID: 25767054

My comment #25262366 references xmachines comment in a previous question and is an excellent way to identify the source of a spamming machine in a networked ebvironment.

 

by: alanhardistyPosted on 2009-11-07 at 15:56:41ID: 25768700

I feel that my comment http://#25262366 is worthy of something.  It answers the question and is a good way to identify spambots.

20120131-EE-VQP-002

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