How to Disable Telnet Published: Mar 14, 2004
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Telnet sends clear text passwords and usernames through logins and should be disabled on all web servers and replaced with SSH.

Telnet sends clear text passwords and usernames through logins and should be disabled on all web servers and replaced with SSH.
Some hosting providers are not disabling telnet by default but you should ensure that it has been turned off as it's a great security risk to your servers. TELNET server listens for incoming messages on port 23, and sends outgoing messages to port 23.

1. Login to your server through SSH and su to root.

2. Type pico /etc/xinetd.d/telnet

3. Look for the line: disable = no and replace with disable = yes

4. Now restart the inetd service: /etc/rc.d/init.d/xinetd restart

5. Turn off it through chkconfig as well because it can still start through that.
/sbin/chkconfig telnet off

6. Scan your server to ensure port 23 is closed.
nmap -sT -O localhost
Also run ps -aux | grep telnet and if you find anything other than "grep telnet" as result kill the process.

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Comments (7)

  • Gravatar - Bit
    Bit 13:51, January 24, 2006
    pico /etc/xinetd.d/telnet<br />
    <br />
    file empty
  • Gravatar - Artin
    Artin 12:06, March 15, 2006
    in Centos 4 you should modify this file :<br />
    /etc/xinetd.d/krb5-telnet
  • Gravatar - Damas
    Damas 22:36, March 19, 2006
    pico /etc/xinetd.d/telnet<br />
    <br />
    file empty <br />
    <br />
    the same problem<br />
    <br />
  • Gravatar - Felipe D.
    Felipe D. 00:23, April 19, 2006
    on CentOS is:<br />
    /etc/xinetd.d/krb5-telnet
  • Gravatar - Rico
    Rico 16:10, August 29, 2006
    I don't know how to log in to my server to disable my telnet. Please advise.
  • Gravatar - Jonathan
    Jonathan 00:22, September 20, 2006
    This is what I see in nano /etc/xinetd.d/krb5-telnet<br />
    <br />
    # default: off<br />
    # description: The kerberized telnet server accepts normal telnet sessions, \<br />
    # but can also use Kerberos 5 authentication.<br />
    service telnet<br />
    {<br />
    flags = REUSE<br />
    socket_type = stream<br />
    wait = no<br />
    user = root<br />
    server = /usr/kerberos/sbin/telnetd<br />
    log_on_failure += USERID<br />
    disable = yes<br />
    }<br />
    <br />
    What Im suppost to change there?
  • Gravatar - Sinan
    Sinan 22:46, October 17, 2006
    on centOS, telnet is disabled by default.

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