Permanently delete files from a flash drive

Solution 1:

The best delete tool that (little) money can buy:

EDIT: To counter the detractors

1. No one mentioned the need for government level security, so arguments with that objective are pointless goalpost shifts. This is good enough for anyone who isn't James Bond or Bruce Wayne. P.S. Governments sanction shredders. What is a hammer but a high velocity shredder?
2. Of course you need to bust up the storage chips within the thumbdrive. I thought that went without saying.
   • "Doctor, I got that bottle of pills from you but they did nothing!"
   • "Did you take the pills out of the bottle."
   • "No."
   • ಠ_ಠ

Furthermore, I did include instruction on how to do a thorough logical wipe of the thumbdrive.

END EDIT

Don't take chances. Flash drives are cheap and yes, data can be recovered from them. I've done it myself. You could DBAN it. You could also cipher /w a few times on a Windows machine (dd if=/dev/zero bs=2048 of=/mnt/disk/file on a *NIX machine). However, hitting things with a hammer is so much more fun and permanent.

Solution 2:

It depends on who your adversary is. If it is a casual user, e.g. friend/coworker/spouse/etc., then preventing regular undelete is good enough: format the flash drive, then fill it with random/non-private files till it's 100% full, then format the flash drive again. Your original sensitive data will be gone for good, and unrecoverable using undelete tools or direct scan of the drive.

However, if your adversary is a major corporation, government, etc., then the only safe course is to destroy the media physically, e.g. burn your flash drive in a high-temperature industrial oven.

Solution 3:

There's an excellent free open-source program called Eraser that removes data by overwriting it with your choice of data patterns - high level security for data erasure.

But - there is a big issue with flash drives when erasing by overwriting. The problem is the "wear leveling" methods used on solid state drives, which writes in a different place each time you add or replace data. There is a full explanation and discussion at Erasing USB key Drives

The short answer - erase the file but also use the "erase open space" function in the Eraser program. This overwrites all unused space, including the earlier version of your file.

Solution 4:

Because of wear leveling of modern flash devices, it's not under your control. You think you've overwritten your data 25 times, it may still be there. If you want to store sensitive data on a flash device, use an encrypted container like truecrypt, so you won't be in trouble when you lose the device (unless you give away the key).