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Old 02-19-2002, 01:50 AM   #1
xtian500
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Registered: Nov 2001
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Question How to Close telnet using ipchains


I set up my firewall using Ipchains, I already closed and denied telnet port 23, Infact when I try to telnet to my mailserver using : telnet mydomain.com simply refuses BUT when I try : telnet mydomain.com 25 it can connect to my mail server
and here's the output :

mydomain# telnet 192.168.20.11 25 or 53
Trying 192.168.20.11
Connected to 192.168.20.11.
Escape character is '^]'.
220 mailserver.mydomain.com ESMTP Sendmail 8.11.0/8.11.0; Tue, 19 Feb 2002 15:26:13 +0800

My objective is to close telnet in any way
here is my telnet firewall setting
/sbin/ipchains -A input -p tcp -s 0/0 -d xxx.xxx.xxx.xxx/yyy.yyy.yyy.yyy 23 -i eth1 -j DENY -l

Any advice would be greatly apprecia

chris
 
Old 02-19-2002, 03:50 AM   #2
raz
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Registered: Apr 2001
Location: London
Posts: 408

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Your using The Telnet client to talk to the SMTP service not the Telnet Service.

Telnet is a command shell service running on default port 23.
You use a telnet client designed to talk to this service on it's default port of 23, however you tell it to talk to port 25 instead so it makes a handshake to that service, nothing to do with telnet.

So that service which you haven't blocked replies.

/Raz
 
  


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