any user has root access

hi
I just found out that any user can log in with an ftp client to sftp with their password and using "root" as user

users who have NO /bin/sh but only /bin/false
using their own password

I used filezilla with SFTP using SSH2, I could not do this with winscp

How can I prevent this from happening?
They can't do much however denying ssh is then a useless function. I don't want users to poke around through the system.

thank you
ronald

Status: 
Closed (fixed)