Visit Our UNIX and Linux User Community


block telnet to specific port


 
Thread Tools Search this Thread
Special Forums IP Networking block telnet to specific port
# 1  
Old 03-19-2002
block telnet to specific port

Hello All

I am running redhat linux 7.2 and would like to know how i can block telnetting to a specified port .

say for example i would like to block telnet acesses to port 80.


regards
Xiamin
# 2  
Old 03-19-2002
This webpage might have the answer for you. Check it out.
http://www.redhat.com/docs/manuals/l...rs-xinetd.html
# 3  
Old 03-20-2002
Hi killserv

That was the most helpful link thank you very much.However my question still reamins unanswered.

regards
Hrishy
# 4  
Old 03-20-2002
What do you mean by "telnet access to port 80"? Incoming? Or outgoing? As far as I am aware, there is no reliable means of knowing which application is producing an incoming request, nor is there any reliable way of blocking outgoing requests based on the application. One of the reasons is that there is no set source port - it just picks one above 1024 that isn't in use, and makes the connection.

Someone let me know if I'm wrong...
# 5  
Old 03-20-2002
Hello

I mean something like this .If there is a incomming request to my server thru a telnet session on port 80.Those packests should be dropped.Hope i am clear....( i think it can be done through iptables currently i am raeding them but this thing is not makin much sense to me. ;-D

regards
Hrishy
# 6  
Old 03-20-2002
First of all, the standard telnet port is 23. If you have telnet enabled through inetd.conf...then it's probably the default port of 23. Now to stop port 80 access it's just a little different.

If you had a webserver available on your node....then a person telnetting to it will get the httpd system banner:

**********************
Whatever Linux v2.2.14
Apache vX.X.XX
etc.
**********************

They can then send a GET command using telnet to pull the HTML...this is exactly what a web browser does.


To stop someone from connecting to this port...all you have to do is go into inetd.conf and comment out the HTTP line....which should look something like this:

http stream tcp nowait nobody ?/var/www/server/httpd httpd

This will shutdown the daemon...or "service"......then no one will be able to connect to it. Restart the inetd daemon by issuing the following command:

killall -HUP inetd

BTW, you will NOT be able to block a telnet'd connection to your port....and allow a web browser. To the firewall, they are essentially the same traffic. [TCP from a 1024+ port]

HTH.

Last edited by thomas.jones; 03-20-2002 at 09:01 PM..

Previous Thread | Next Thread
Test Your Knowledge in Computers #815
Difficulty: Medium
In CSS, E[foo] matches an E element with a 'foo' class name.
True or False?

10 More Discussions You Might Find Interesting

1. Solaris

Block port for all except for one specific ip in Solaris11.4

Hi, I need to block ssh port 22 from all the servers except one server ip. Until solaris11.3 and below, I used to do like below(under /etc/ipf/ipf.conf),and it's working fine pass in quick from $server_ip to any port=22 block in quick from any to any port=22 But I tried almost same in... (1 Reply)
Discussion started by: Sumanthsv
1 Replies

2. UNIX for Dummies Questions & Answers

telnet echoing 'trying ip' but no port number

Hi, Well this is probably a silly one that I should know...but I don't ! I'm telnetting to various ports from a shell script and the telnet is echoing back that it's 'trying xxx.xx.xx.xx...' but not the port number it's trying! Any help much appreciated Thanks (1 Reply)
Discussion started by: Grueben
1 Replies

3. IP Networking

telnet for port 5433 is not working while it works for port 22

Hi, I am trying to set up a dev environment and I have Ubuntu server (10.16.1.92) and a CentOS VM (10.16.3.235) on this. On the CentOS I have a program running on port 5433. Now my problem is that I am unable to telnet this port from another Windows server whereas I can telnet port 22 from... (5 Replies)
Discussion started by: rishav
5 Replies

4. Red Hat

telnet port 23

My linux version is 2.6.18-194.e14 (Oracle enterprise linux). Could you please tell me how to enable telnet on the server. When I try to connect the server through another pc using telnet it is throwing error. Connecting To <ip address>...Could not open connection to the host, on port 23.... (3 Replies)
Discussion started by: oradba_arun
3 Replies

5. Cybersecurity

Can't telnet to port 25 on the host.

Hi, we have recently setup a new UNIX server with solaris 10 and I am having issue with with SMTP/sendmail. telnet localhost 25 --- works telnet hostname.domain.com 25 -- does not work. # telnet hostname.domain.com 25 Trying 10.122.1.111... telnet: Unable to connect to remote host:... (1 Reply)
Discussion started by: esmgr
1 Replies

6. Windows & DOS: Issues & Discussions

Telnet to a serial port

Hello all. I have an old computer with M$-DOS 7. I want to use it like a dumb terminal, with telnet. I need to connect it to my desktop These are my questions: How can i configure the serial port on dos? How can i telnet form dos to the serial port? How can i set up a telnet server on the... (12 Replies)
Discussion started by: mghis
12 Replies

7. AIX

Telnet to port

can some one help me ? what happens when we telnet to a port ? example telnet 192.168.0.xx 1234 where 1234 is a port number Thank you (5 Replies)
Discussion started by: anwesh
5 Replies

8. Shell Programming and Scripting

Telnet IP and Port Script

Hi, I would like to create a simple script that will telnet a number of IP and Ports one after the other to confirm connectivity to those addresses. I don't need to log on, just output to a file what the response is, i.e Escape Character, connectivity refused etc. Complete newbie to... (6 Replies)
Discussion started by: asou
6 Replies

9. UNIX for Advanced & Expert Users

telnet on specific port??

Hi all, I have a problem. I have machine names and their IP addresses in /etc/hosts file. My application does telnet on that machine host name. The application does not uses IP address for tenet. It will fetch the host name from /etc/hosts file. Now the telnet server runs on customized port.... (6 Replies)
Discussion started by: zing_foru
6 Replies

10. Solaris

disabled telnet now need port 23 or port 22

we disabled telnet on solaris 9 via previous a thread. We use CMS (call management system) supervisor which used port 23 (telnet). We cannot use telnet via local directive and it was shut down as stated when we shut down telnet in the inetd file. I cannot now log into the CMS box since port 23 is... (3 Replies)
Discussion started by: panzerkw
3 Replies

Featured Tech Videos