Disable root login for SSH on Ubuntu:

Edit this file:
sudo nano /etc/ssh/sshd_config

Replace:
#PermitRootLogin prohibit-password
with:
PermitRootLogin no

Save with Ctrl+X

Then lock the root user by:
sudo passwd root -ld

*Also lock these users while at it:
sudo passwd games -ld
sudo passwd news -ld
sudo passwd www-data -ld
sudo passwd mail -ld

Can see if a user is locked by if the /etc/shadow file has a ! for the user rather then a * or a password.

Then restart OpenSSH server by:
sudo systemctl restart ssh

You should no longer be able to access root.

Source 1 | Source 2 | Date: April 19th 2024

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