How to Secure SSH

Overview

This document lists several helpful changes that you can make to your server to improve SSH security. We strongly recommend that you restrict and properly configure Secure Shell (SSH) access in order to secure your server.

Be careful who you grant SSH access to

If a user does not need SSH access, do not grant them access. To remove a user’s SSH access, use WHM’s Manage Shell Access interface (WHM » Home » Account Functions » Manage Shell Access).

Some users may need SSH access, but only need access to files in their home directory. We recommend that you assign a jailed shell environment to these users. For more information about jailed shells, read our VirtFS - Jailed Shell documentation.

Set an SSH Legal Message

The system can display an SSH legal message (message of the day, or motd) whenever someone logs in to your server through SSH.

To set the message, use your preferred text editor to edit the /etc/motd file and save your changes. For example, one of our technical analysts uses the following message:

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ALERT! You have entered a secured area! The system has recorded
your IP and login information, and it has notified the administrator.

This system is restricted to authorized access only. All activities on
this system are recorded and logged. The system administrator will fully
investigate and report unauthorized activity to the appropriate law
enforcement agencies.

Use SSH Keys

You can disable password authentication for SSH on your server, which will force users to log in through SSH with keys instead of passwords.

To do this, perform the following:

1. Use WHM’s Manage root’s SSH Keys interface (WHM » Home » Security Center » Manage root’s SSH Keys) to generate and download a key for the root user.

2. Use WHM’s SSH Password Authorization Tweak interface (WHM » Home » Security Center » SSH Password Authorization Tweak) to disable password authentication for SSH.

Strengthen SSH security

The /etc/ssh/sshd_config file contains your server’s configuration settings for SSH. We recommend that you change the following settings:

• Port — The port number on which the sshd daemon listens for connections. The highest acceptable value is 49151.

  Note:

  We recommend that you use a privileged port of 1 - 1023 that another service does not currently use. Only the root user can bind to ports 1 - 1023. Anyone can use the unprivileged ports of 1024 and greater.

• Protocol — The SSH protocol that your server uses. We recommend that you change this value to 2.

• ListenAddress — The IP address on which the sshd daemon listens for connections. Your server must own this IP address. We strongly recommend that you do not use your main shared IP address for this value. You can create a custom DNS entry specifically for the new SSH IP address. To do so, create a zone file (for example, ssh.example.com) and add an A entry to the zone file for the new nameserver entry.

• PermitRootLogin — This option specifies whether you wish to allow people to directly log in to SSH as the root user. We strongly recommend that you set this value to no.

Edit the sshd_config file

To configure the /etc/ssh/sshd_config file in order to tighten your server’s security, perform the following steps:

1. Log in to your server as the root user via SSH. If your server does not allow direct root logins to SSH, log in as your wheel user and use the su command to become the root user.

2. Back up the sshd_config file with the following command:

   cp /etc/ssh/sshd_config /etc/ssh/sshd_config.bak`date +%F`

3. Open the /etc/ssh/sshd_config file with a text editor.

4. To change a parameter in the sshd_config file, uncomment the line that contains the parameter. To do this, remove the number-sign character (#) and change the value for the line.

   Important:

   If you change the default SSH port, you must update your server’s firewall configuration to allow traffic to the new port. For more information about firewall configuration, read our How to Configure Your Firewall for cPanel & WHM Services documentation.

   For example, the default SSH port appears in a line similar to the following example:

   #Port 22

   To change the SSH port to 456, edit that line to resemble the following example:

   Port 456

After you configure SSH, run the /scripts/restart_sshd script or the service sshd restart command to restart the SSH daemon.

After you restart SSH, log out of your server and log in again with the user, IP address, and port number that you specified in the sshd_config file.

https://example.com:2087/scripts2/doautofixer?autofix=safesshrestart

Example sshd_config File