RE:Prevent Telnet to port 25

  • From: "Jamie A. Byrnes" <jabyrnes@xxxxxxxxxxxxxxxxx>
  • To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
  • Date: Sat, 12 Apr 2003 11:52:02 +0930

Just to expand on what Mark has said, you can block all ports other than
25 from reaching port 25 on your mail server, remembering that if you
are doing external DNS lookups you will need to open up DNS to DNS as
well. But a smart telnet or low level packet program like Mudge's great
netcat can easily fake its sending port number to bypass this.

 

But it is still worthwhile as it will slow down the spammer scanners
looking for open relays.

 

Jamie.

-----Original Message-----
From: Mark Fugatt [mailto:mark@xxxxxxxxx] 
Sent: Saturday, 12 April 2003 12:11 AM
To: [ExchangeList]
Subject: [exchangelist] RE:Prevent Telnet to port 25

 

http://www.MSExchange.org/

I think they were looking at a way to stop people from using telnet to
connect to port 25, and the only way to do that is to block port 25 and
then you will not receive any mail from the outside world.

 

Mark Fugatt 
MCT, MCSE, Microsoft Exchange MVP 
Pentech Office Solutions Inc 
Tel:  585 586 3890 
Fax: 585 249 0316 
www.4mcts.com <http://www.4mcts.com/>  
www.exchangetrainer.com <http://www.exchangetrainer.com/>  

 

 

  _____  

From: Joshua M. Etterman [mailto:jetterman@xxxxxxxxxxxxxxxxxxxxxxxxxxxx]

Sent: Friday, April 11, 2003 10:39 AM
To: [ExchangeList]

http://www.MSExchange.org/

I don't quite remember how I did it, but you can't telnet into my
exchange server (Ex2k + Win2kAdv + latest SP's)

 

I think I went ahead and disabled telnet ability within Win2k. 

 

Are you talking about a non-telnet port?

 

--

Joshua Etterman

Complete College Solutions

 

513 W. Chocolate Ave.

Hershey, PA 17033

 

Phone: (717) 508-2000

Fax: (717) 508-2001

E-mail: jetterman@xxxxxxxxxxxxxxxxxxxxxxxxxxxx

 

-----Original Message-----
From: Jamie A. Byrnes [mailto:jabyrnes@xxxxxxxxxxxxxxxxx] 
Sent: Friday, April 11, 2003 1:56 AM
To: [ExchangeList]
Subject: [exchangelist] RE:Prevent Telnet to port 25

 

The short answer is no.

 

The longer answer is that you can set firewall rules to try to do this,
but it is simple to get around.

 

But the question is what are you trying to achieve?

 

 

Jamie.

 

 

-----Original Message-----
From: Meral KESKINER [mailto:MeralK@xxxxxxxxxxxx] 
Sent: Friday, 11 April 2003 3:19 PM
To: [ExchangeList]
Subject: [exchangelist] Prevent Telnet to port 25

 

http://www.MSExchange.org/

Hi all,

 

    Is there a way to prevent telnet to my mail server?

 

Thanks,

 

Regards,

 

 

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