One option is to fully encrypt the external drive and lock it with password.
Lock usb drive mac.
On said site they ll find the oddly named rohos logon key which is a new the os x version at least downloadable application that turns the usb drive into a key that can lock a mac up tighter.
Fortunately mac os x provides a few native solutions to help you protect your data on external hard drives.
The best part about this application is that it s available for both windows and macos devices.
When you see your removable disk in the left panel right click it and select encrypt from the contextual menu.
Insert your usb drive into the mac and open a finder window.
Set up usb lock on pc or mac rohos key logon is a software that can program a usb flash drive a mobile phone or even a bluetooth device to act as the key to unlock your system.
In the filevault window you can set a password by typing it in twice as well as set a password hint.
Connect the usb flash drive to your mac and find its disk icon on the desktop or finder sidebar then right click and select encrypt usb stick name from the context menu.
Encrypt and protect a storage device with a password in disk utility on mac.
If you do not see the encryption option in the drop down menu your usb flash drive has not been formatted using the guid partition map.
But in order to do so the external drive should be using the guid partition table gpt scheme.
In the sidebar select the storage device you want to.