topic Re: Disable telnet from certain ip in Operating System - Linux

Disable telnet from certain ip

R.O. — Wed, 03 Dec 2003 03:38:48 GMT

Hi,

I want to disable telnet in a linux box, but only from certains IpÂ´s. I know to do this in HPUX, in the file /var/adm/inetd.sec, but how can I do it in red hat?

Th

Re: Disable telnet from certain ip

Mark Grant — Wed, 03 Dec 2003 03:51:04 GMT

If you use Red Hat or don't mind installing xinetd instead of inetd then you can look at /etc/xinetd.d/telnet and specify an "only_from" line. You would have something like "only_from hostname1 hostname2 etc"

If you are not using xinetd, I think you are ought of luck.

Re: Disable telnet from certain ip

R.O. — Wed, 03 Dec 2003 03:59:52 GMT

Hi,

I use xinetd, but wat I want is to specify "not from" or something like this, instead of "only from"

Thanks and regards

Re: Disable telnet from certain ip

R.O. — Wed, 03 Dec 2003 04:08:48 GMT

Hi,

IÂ´ve found it. Is putting the clause "no_access" in telnet file.

Thxs & regar

Re: Disable telnet from certain ip

James Specht — Wed, 03 Dec 2003 08:49:18 GMT

There are two files in /etc. hosts.allow and hosts.deny. In hosts.deny you add the following.

telnet:ALL

This denies telnet to all systems.

In hosts.allow you can add.

telnet:123.123.123.
telnet:servera.abc.com

This will allow only those systems/subnets/IPs listed in the hosts.allow to access your system using telnet.

--Jim

Re: Disable telnet from certain ip

Michael Schulte zur Sur — Wed, 03 Dec 2003 10:26:51 GMT

Hi,

my idea would be to add this to /etc/profile:
REMOTEIP=expr "`who -m`" : ".*($.*$).*"
case ${REMOTEIP} in
"10.0.0.1"|"10.0.0.2") echo sorry!!;exit;;
esac

greetings,

Michael

Re: Disable telnet from certain ip

Stuart Browne — Wed, 03 Dec 2003 19:33:29 GMT

3 ways to do it.

James mentioned one.

You found a second.

The third is just to firewall it out with 'iptables', i.e.:

iptables -IN INPUT -j DROP -s -p tcp --dport 23

Fun huh? :)

Re: Disable telnet from certain ip

sujith_2 — Tue, 11 May 2004 02:32:18 GMT

Hi,
I have done it by using webmin utility ( GUI Based System Admin Utility )

In this utility login as root and go to Networking===>Linux Firewall menu

And make one chain to reject from a particular ipaddress. Eg:

Reject If protocol is TCP and source is 192.168.178.134 and input interface is eth1 and destination port is 23

Its very easy...

Sujith

Re: Disable telnet from certain ip

Mark Travis — Tue, 11 May 2004 14:51:38 GMT

The easiest way is tcp wrappers.

man 5 hosts_access on newish redhat systems will take you to the man page.

You can also look at /etc/hosts.allow and /etc/hosts.deny to see a template.

Re: Disable telnet from certain ip

Mobeen_1 — Thu, 13 May 2004 01:06:23 GMT

HO,
I think the best to accomplish this in your existing setup would be using the /etc/hosts.allow and /etc/hosts.deny files.

Edit the file /etc/hosts.allow and make an entry ALL. Then edit file /etc/hosts.deny and make an entry for all the IP addresses which need to be blocked.

Let me know if you have any specific questions.

regards
Mobeen