Secure Your SSH Access

To restrict and secure SSH access, bind sshd to a single IP that is different than the main IP to the server, and on a different port than port 22.

SSH into server and login as root.

At command prompt type: pico /etc/ssh/sshd_config

Scroll down to the section of the file that looks like this:

#Port 22
#Protocol 2, 1
#ListenAddress 0.0.0.0
#ListenAddress ::

Uncomment and change

#Port 22

to look like

Port 5678 (choose your own 4 to 5 digit port number (49151 is the highest port number)

Uncomment and change

#Protocol 2, 1

to look like

Protocol 2

Uncomment and change

#ListenAddress 0.0.0.0

to look like

ListenAddress 123.123.123.15 (use one of your own IP Addresses that has been assigned to your server)

Note 1: If you would like to disable direct Root Login, scroll down until you find

#PermitRootLogin yes

and uncomment it and make it look like

PermitRootLogin no

Save by pressing Ctrl o on your keyboard, and then exit by pressing Ctrl x on your keyboard.

Now restart SSH

At command prompt type: /etc/rc.d/init.d/sshd restart

Exit out of SSH, and then re-login to SSH using the new IP, and the new port.

Note: If you should have any problems, just Telnet into your server, fix the problem, then SSH in again. Telnet is a very unsecure protocol, so change your root password after you use it.

Disable Telnet

To disable telnet, SSH into server and login as root.

At command prompt type: pico -w /etc/xinetd.d/telnet

change disable = no to disable = yes

Save and Exit

At command prompt type: /etc/init.d/xinetd restart

Server e-mail everytime someone logs in as root

To have the server e-mail you everytime someone logs in as root, SSH into server and login as root.

At command prompt type: pico .bash_profile

Scroll down to the end of the file and add the following line:

echo ‘ALERT – Root Shell Access on:’ `date` `who` | mail -s “Alert: Root Access from `who | awk ‘{print $6}’`” your@email.com

Save and exit.

Set an SSH Legal Message

To an SSH legal message, SSH into server and login as root.

At command prompt type: pico /etc/motd

Enter your message, save and exit.

Note: I use the following message…

ALERT! You are entering a secured area! Your IP and login information
have been recorded. System administration has been notified.

This system is restricted to authorized access only. All activities on
this system are recorded and logged. Unauthorized access will be fully
investigated and reported to the appropriate law enforcement agencies.

Now everytime someone logs in as root, they will see this message.