Secure the files on a USB thumb drive in case you lose it

Secure the files on a USB flash drive by encrypting them using an Apple Mac

USB thumb drives (flash drives) are great for carrying around files, but they are easily lost. What if someone found your thumb drive? Follow these steps to secure your files and stay safe.

With capacities up to 128GB, thumb drives (flash drives or pen drives), are convenient for storing files you want to move between computers, such as home and work.

They are handy for freeing up space on your Mac’s disk, and they are useful when you want to give someone a bunch of files, but don’t want to send them over the internet.

Count yourself lucky if you have not lost one because it is all too easy to do. The finder could then access your files, which could contain private information that you don’t want others to see.

Store files in a disk image

There are two ways to secure the files on a thumb drive and both involve encrypting them. One method is to create an encrypted disk image - a .dmg file.

I showed how to create encrypted .dmg files in this article. The .dmg was stored on the Mac’s disk, but all you would need to do is to copy it to the thumb drive after creating it.

No-one can open the .dmg file without the password, so any files you put in it are safe.

This method has the advantage of enabling you to use part of the storage as normal and part as encrypted and secure.

If you create the .dmg file just slightly smaller than the capacity of the thumb drive, it will leave a bit of space into which you could put a text file with your email and phone number, and a request for the finder of the lost thumb drive to return it.

Encrypt the drive

The whole thumb drive can be encrypted and this is the most convenient way to secure your files. Files are encrypted as they are written to the thumb drive and decrypted when they are read. This is totally transparent to you and the drive works as normal.

Without the password though, it cannot be unlocked or accessed.

1 Run Disk Utility

Thumb drives are almost always formatted using the FAT filing system so that they work on PCs and Macs. This is convenient for thieves too. The thumb drive must be formatted before it can be encrypted

Open Disk Utility in the Utilities folder (click Go, Utilities).

Select the thumb drive in the list on the left and then click Erase.

Erase a drive using Disk Utility in macOS Sierra on the Apple Mac

2 Erase the drive

The format must be set to Mac OS Extended (Journaled).

The scheme must be set to GUID Partition map.

Click Erase to begin.

Format a disk or drive using Disk Utility in macOS Sierra on the Apple Mac

3 Encrypt the drive

After formatting it, Ctrl+click the thumb drive icon on the desktop and select Encrypt.

Encrypt a disk using macOS Sierra on the Apple Mac

4 Password protect it

All that remains is to think of a secure password and enter it.

Add a hint, just in case you forget the password. Without it you will not be able to access your files.

Encrypt a disk using macOS Sierra on the Apple Mac

5 Open the drive

After encrypting it, when you try to open the thumb drive you are asked for the password. This is remembered until you eject the thumb drive or switch off the computer. Then the thumb drive is locked.

Access an encrypted drive by entering the password on the Apple Mac

Now there is no excuse for leaving thumb drives around with unprotected files. Encrypt them!

6 Decrypt and encrypted drive

Suppose you want to remove the encryption from a drive so it can be used normally again. This is straightforward and you just right click the drive and select the Decrypt option.

You are asked for the password and then it begins removing the encryption.

Neither encryption nor decryption deletes the files on the drive. The files that were there before are there afterwards.

Decrypt an encrypted disk on the Apple Mac using macOS Sierra

As you can see, encryption and decryption is easy. Why not use it?



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