I have a desktop computer in my home network with SSH server running on it. Using another computer in my private and local network (class C IP addresses: e.g., 192.168.0.2, etc) I sometimes use SSH to enter into the desktop PC with command
ssh <user_name>@192.168.0.2 and work remotely.
I am wondering if someone from the internet (thus from outside my local network) may gather access to my desktop computer via SSH (i.e., by guessing the user_name and password). Is this SSH server/service accessible from the outside if the username and password are known? Or is impossible to gather access without knowing other details such as the IP of the network gateway and others.
My goal is to keep using SSH internally in my local network but at the same time block any possibility to gain access to any device in the network from the outside. So securely use SSH.