Those directions are incomplete and
leave you VERY vulnerable still. Follow my directions in my post on this thread
https://forums.macrumors.com/posts/8792161/
There is a section if you are doing it over an SSH client or from MobileTerminal.
The part that the link you were referring to is missing is changing the root password. It only instructs changing the mobile password. With root access the hacker has full access to your device still. You need to change both.
You read my post. You need to 'su root' to switch to root and then run 'passwd' again to change that password too.
I can't stress how important this extra step is. If you only follow the directions on that link you are
not at all safe. You must follow my directions in this thread and change BOTH passwords (you can change them to the same thing, just not 'alpine').