sudo su gives root without prompting for a password

["Benedict Verheyen" <linux4bene@pandora.be>]

Hi,

i recently removed the SUID bit from /bin/su.
The permissions now look like this: -rwxr-x---
Now i can just type "sudo su" to become root and no password
is asked. Previously i needed to type the root password
when using su. As a normal user, i now cannot run su anymore
which is ok for me.
The permissions of sudo are: -rwsr-x---

My /etc/sudoers file looks like this:
root ALL=(ALL)ALL
benedict ALL= NOPASSWD: /usr/bin/find, /bin/cpio,
/home/benedict/scripts/backup, /bin/echo, PASSWD: ALL

The entries with NOPASSWD are because of a backup script.
So why don't i need to type a password for running "sudo su".
It just doesn't feel right the way it's now.

Thanks,
Benedict