USB – How to Make a USB Drive Read Only

The easiest way to troubleshoot the problem with your SATA hard drive would be to buy a USB SATA external hard drive enclosure. These devices are very inexpensive. Connect the portable hard drive enclosure to another computer.

• Is it properly detected as an external hard drive?
• Can you browse the files and folders on the hard drive?

If the answer to these questions is yes, then you probably have a problem with your old PC and not the SATA hard drive, and judging from your frustration with your old PC, it is probably time for you to buy a new computer.

Answers to questions like this depend on the so-called "attack model" that you want to be protected from. In other words, will the user actively try to overcome your protection? Or is the protection there just to warn the user, which you trust to be honest with respect to the read-only setting and not try to overcome it?

In the second case, setting the read-only flag in the file properties should be enough. When the user will open your file, the program will tell him that the file is read-only and they cannot save it. If the user is honest, he will not do anything.

The first case is much more difficult, and actually there is very little to do about it. Giving a USB pen to someone is much like giving them a paper sheet with pencil writing on it. There is no way you can prevent your user from erasing some part of your sheet and writing again on it, no matter what you write in it (in this metaphor there is no equivalent of the pen; everything that you write on a USB pen is erasable and re-writable; if you want to have a pen equivalent, you have to write on a CD-ROM).

In this metaphor, setting the read-only flag is no different from writing (in pencil): "Please, do not erase of modify things here". If the user is honest, they do not do it. But there is no technical mean that prevents them from doing that if they are not honest.

So, in this case, the answer is basically "no".

There is a partial workaround that may or may not be applicable to your case: you can add a digital signature to the file you want to protect. The user is still able to modify the file, but thanks to the digital signature this leaves evidence that the file was modified. However this is a very broad topic, which has in turn other caveats, and it would be off-topic to discuss it here.