At the end of a Debian installation you are asked whether you want to use
"shadow passwords" or not. With Linux Mint is not the case. But there is
still the possibility to set "shadow passwords".
In a terminal you can type:
~ $ sudo shadowconfig on
Passwords will be kept now not in the file '/etc/passwd' but in '/etc/shadow'.
Only root and the group shadow have read access to this file.
No user will be able to grab a copy of this file to run a password cracker
You can use the command `shadowconfig' in Mint at any time to change between
"shadow passwords" and normal passwords.
shadowconfig on | off
The idea is now well within the Mint installation ask that question too.
The user can then make the appropriate setting.