Support LQ: Use code LQ3 and save $3 on Domain Registration
Go Back > Forums > Linux Forums > Linux - Security
User Name
Linux - Security This forum is for all security related questions.
Questions, tips, system compromises, firewalls, etc. are all included here.


  Search this Thread
Old 02-19-2002, 02:50 AM   #1
LQ Newbie
Registered: Nov 2001
Posts: 15

Rep: Reputation: 0
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 simply refuses BUT when I try : telnet 25 it can connect to my mail server
and here's the output :

mydomain# telnet 25 or 53
Connected to
Escape character is '^]'.
220 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 23 -i eth1 -j DENY -l

Any advice would be greatly apprecia

Old 02-19-2002, 04:50 AM   #2
Registered: Apr 2001
Location: London
Posts: 408

Rep: Reputation: 31
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.



Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
How do I setup telnet on Fedorac1 so I can telnet to it from winxp? mman49 Fedora 6 05-02-2004 01:40 PM
can not telnet localhost 25 but telnet 25 exper Linux - Software 0 02-25-2004 06:13 AM
HLDS closes when I close telnet MarleyGPN Linux - General 1 04-26-2003 06:34 PM
enable telnet but can't telnet from the computer guanyu Linux - Networking 8 08-26-2002 07:34 AM
telnet local but no-telnet via internet blacksheep Linux - Networking 7 11-26-2001 03:33 PM

All times are GMT -5. The time now is 10:10 PM.

Main Menu
Write for LQ is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration