The OpenSSH server can be configured to hide its version number from clients, making it more difficult for attackers to target known vulnerabilities in specific versions of the software. This can be done by editing the OpenSSH server configuration file, usually located at /etc/ssh/sshd_config.
To hide the version number, add the following line to the sshd_config file:
# Hide OpenSSH version number
ServerSignature no
Save the file and then restart the OpenSSH server to apply the changes:
sudo service ssh restart
On some systems, the command to restart the OpenSSH server may be different, such as sudo systemctl restart ssh. You can check the documentation for your specific Linux distribution for more information.
Note that hiding the version number from clients is only one aspect of securing the OpenSSH server. You should also follow best practices for securing the server, such as using strong passwords, configuring firewalls, and keeping the software up to date.