What is SSH?

The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Typical applications include remote command-line, login, and remote command execution, but any network service can be secured with SSH.

What is a SSH banner?

The SSH banner is used to add a warning to the connection, when a user connects to your SSH he well see a message like this one:

By default, no banner is showed, and the option is disabled. It is also useful to display a legal notice if required by local law.

How to add a ssh banner at login?

So the first thing that we have to do is to edit sshd_conf in /etc/ssh/

# How to edint sshd_config
sudo pico /etc/ssh/sshd_config
Code language: PHP (php)

Find the following text

# no default banner path
# Banner none
Code language: PHP (php)

Add after # Banner none on a new line:

Banner /etc/issue.net

Now you are going to have a file like this one

Now it’s time to write what the banner is going to tell us, edit /etc/issue.net

# Edit /etc/issue.net
sudo pico /etc/issue.net
Code language: PHP (php)

Now lets add some text:

# If you have entered here by accident please leave the ssh session
Code language: PHP (php)

It’s time to save the document and restart the sshd service

# restart sshd service
service sshd restart
Code language: PHP (php)

Now on every new connection the ssh session will display the text like so:

Conclusion

In conclusion we can say that this is a good method to give some information to an entering person on the ssh session, but would you use it? What would you write?

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