From: John Swope (johns@akorn.net)
Date: Thu Mar 04 2004 - 00:08:49 EST
All,
I work for an enterprise email security company and saw something rather
odd just the other day and this might be related.
I was troubleshooting a customer's mail environment, they were an Exchange
shop and our appliance is Unix based. I was noticing a 5 second delay
between when I telnetted to port 25 and when the Exchange server actually
presented it's 220 banner.
Odd, hosts were connected via 100 Base-T, exchange server was not
overloaded. No lost packets. What gives...
Ran tcpdump -X -s1600 host exchange.customer.com
Notice, no restriction on ports or types of traffic just on host...
I noticed the Exchange server was performing 3 NBT broadcasts to try to
resolve the LMHOST name of my box. Naturally it did not work because I'm a
Unix box not running Samba.
So, could the exchange server in your case be doing the same? Would it
explain the results? Is the PIX allowing all traffic from Exchange to
external network? I realize that I was seeing broadcast traffic and one of
the posts in the thread mentioned the boxes are separated by a PIX, just
throwing this in as something worth checking...
HTH,
BJ
At 05:45 AM 03/03/04, Deniz CEVIK wrote:
> Hi all,
>
>This host is behind the cisco pix firewall. I have scanned this host using
>several portscan tools. These tools show that only two ports are open. (SMTP
>and POP3). Strange think is, if you don't establish the TCP connection to
>one of these open ports, before run the "nbtstat" command, you get nothing.
>But if you open a tcp connection and after that run nbtstat command, you can
>see the details of netbios information of machine.
>
>Nbtstat command is sending packets to udp 137 port of destination. As far as
>I see, firewall is accepting udp packets, if there is an established tcp
>connection from same source to same destination as in udp connection
>request. I think there is a configuration problem in the customer firewall.
>For further analysis I requested firewall configuration and logs.
>
>Thanks for your helps.
>
>PS: HADXM is the hostname of the machine. I have modified some information
>in outputs before I posted the message.
>
>BR.
>
>
>-----Original Message-----
>From: jamesworld@intelligencia.com [mailto:jamesworld@intelligencia.com]
>Sent: Wednesday, March 03, 2004 4:17 AM
>To: Deniz CEVIK
>Cc: pen-test@securityfocus.com
>Subject: Re: Exhange 2003
>
>Did you try
>
>netstat -an
>
>And see what ports were listening?
>
>Is there a local IP filtering policy active? You mentioned only 2 ports as
>being active 25 and 100. Perhaps there is a local IP policy only allowing
>those ports. Perhaps the port 100 was supposed to be port 110 for POP3
>mail access and they typod the entry. Good of you to find their
>misconfiguration for them :-)
>
>Did you run fport (foundstone)? If you've never used fport, you should add
>it to your arsenal.
>
>Hopefully HADXM is the username that you are using. If not, look into the
>host being compromised.
>
>If you have more, post it to us.
>
>Cheers,
>-James
>
>At 08:29 03/02/2004, Deniz CEVIK wrote:
> >Hi All,
> >
> >While we are testing our customer network, we faced with strange problem.
>We
> >are testing exchange 2003 server externally. When we controlled open
> >services with port scan, I saw that only two ports (25 and 100) are shown
>as
> >open. Before I run the portscan, I have controlled the server with
>"nbtstat"
> >command of windows. It returned error messages as below.
> >
> >nbtstat -A EXCH_IP
> >
> >Local Area Connection:
> >Node IpAddress: [MY_MACHINE] Scope Id: []
> >
> > Host not found.
> >
> >After the port scan is finished, in order to see the banner information of
> >mail server, I opened the connection to port 25 using telnet command
>(telnet
> >EXCH_IP 25). Same time when I run "nbtstat -A" command from another window
> >by mistake and I saw that below output.
> >
> >nbtstat -A EXCH_IP
> >
> >Local Area Connection:
> >Node IpAddress: [MY_MACHINE] Scope Id: []
> >
> > NetBIOS Remote Machine Name Table
> >
> > Name Type Status
> > ---------------------------------------------
> > HADXM <1F> UNIQUE Registered
> > HADXM <00> UNIQUE Registered
> > HADXM <20> UNIQUE Registered
> > EXCHANGE <00> GROUP Registered
> > EXCHANGE <1C> GROUP Registered
> > EXCHANGE <1B> UNIQUE Registered
> > EXCHANGE <1E> GROUP Registered
> > HADXM <03> UNIQUE Registered
> > ADMINISTRATOR <03> UNIQUE Registered
> > EXCHANGE <1D> UNIQUE Registered
> > ..__MSBROWSE__. <01> GROUP Registered
> > HADXM <6A> UNIQUE Registered
> > HADXM <87> UNIQUE Registered
> >
> > MAC Address = MAC_ADDRESS_OF_EXCHANGE
> >
> >If there isn't any connection to open port of the server you can't see this
> >nbtstat outputs.
> >
> >Has any body faced with same situations before?
> >
> >BR
> >
> >
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>
>
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