What Knoppix version; what install type?
Permissions to access drives is set by /etc/fstab; permissions can be set to deny users write access or total access to drives. 'mount' command is always reseved for su only; on CD the script run by the cd icons mounts the drive as su since there is no su password it can do this without any action by the user. On a HD install with a root password set and users other than 'knoppix' this is not so. User knoppix on CD or on Knoppix type hd install has full sudo priviladges with no password required.