Root login attempt ssh:notty

Hello

I had literally 5 non terminal login attempts to root, "Authentication failure for root via sshd from 59.47.112.161 ssh:notty", before Fail2ban did it's job and blocked the IP. I am aware that this is common if the ssh server is exposed to the internet but ssh access is supposed to only be available to my internal network, I VPN into the network if I need to do anything via ssh. I also don't have thousands log entries for failed root login attempts so it doesn't indicate that I have a config error but you never know.

Can anyone possibly shed some light on how/why this would happen?