You can disable
autofs if you don't need it. This will prevent to mount automatically removable media or NFS filesystems.
You can simply write a udev rule to disable automounting.
First, create the file
sudo vi /etc/udev/rules.d/85-no-automount.rules
and add the following lines:
Restart the service:
sudo service udev restart
This will prevent any USB device from being mounted by the udisksd daemon. If the service didn't worked, you might need to reboot the server.