How can I securely wipe the unused space on my external HDD without deleting its existing contents?

[matrixgravity]

Hi. I have a 1TB External HDD that contains important files on there, and I'd like to know how I can safely wipe the unused space on this HDD to ensure that there is no retrievable data on it. What I mean is, there are some files that I had deleted in the past on this particular HDD that I'd like to ensure are no longer retrievable, so that's basically the data that I want to wipe without affecting any of the existing backup files that I already have on there, if that makes sense. What is the safest approach to doing this? Thank you.

 

[Phillip Corcoran]

So it's securely erasing the "free space" you really mean - - that's what it's called - - free space.

You can do that with the "Drive Wiper" feature in the free & very popular cleanup utility called CCleaner:

https://filehippo.com/download_ccleaner/

Install CCleaner.

Open CCleaner.

Click on "Tools" >>> "Drive Wiper"

The rest is self-explanatory & should be intuitive to any competent person.

The "3 passes" option in security options should be sufficient to prevent normal recovery with recovery software, or choose "7 passes" if you're really paranoid, but be aware that more passes will take much longer & you can't use your PC for anything else while the cleaner is running. "7 passes" is overkill for most people in my opinion.

Also more passes equates to more wear and tear on the drive over time.

 

[RolandJS]

The safest way to use ccleaner is to keep everything closed, turned off, that can be closed or turned off, regarding foreground and background programs and utilities during any such free space wipe -- that also might mean being disconnect from the internet during such free space wipe. And, if you really want to be safe, make full images of your OS and Data partitions before and after the free space wipe.
** I just now saw it's an external HD, not the OS internal HD, my advice obviously needs to be adjusted to suit the situation! **

 

[BFG-9000]

Download sdelete from Microsoft.

In a command prompt, run sdelete -c D: /accepteula
where D: is the letter of the HDD you want to clean the free space of.

It works by creating files the size of all the free space filled with zeroes, then 255s, then random data, which securely cleans the free space to military DoD standards.

Alternately you can use Windows' built in cipher command like so:
cipher /w:E
where E is the letter of the drive or partition you want to wipe free space on (I couldn't use D as the example here because this board translates that to a smiley! 😀)

 

[USAFRet]

Whatever method you choose for this, please make a full drive backup before you click the GO button.

Just in case.

 

[CountMike]

I'm using this one: http://www.majorgeeks.com/files/details/alternate_file_shredder.html for some time now just for shredding unused space, safe and no problems with it. Adjustable for number of passes, 2 is usually quite enough.

 

[Phillip Corcoran]

Well I use Ccleaner's Drive Wiper because I already have it installed as a daily cleanup tool, so I don't see any point in me installing a separate utility just to wipe free space when CCleaner can do the job. I'v never had any problems with it,

No need to disable antivirus, turn anything off or any of that nonsense as suggested by one poster - - it runs fine without all that malarky.

 

[CountMike]

I don't like programs that do or try to do everything, simple program for one purpose that does it well is my favorite.

 

[RolandJS]

"No need to disable antivirus, turn anything off or any of that nonsense as suggested by one poster - - it runs fine without all that malarky."
True for most circumstances! Turning off AM/AV, I never called for that, is not necessary. However, if one is over-writing free space (wiping free space), I recommend not having anything running that is not necessary for work or play only because in another thread in another forum - a user lost parts of his/her data folders during such a free-space wipe. Everything else done by ccleaner or similar utility does not need foreground or background stuff turned off.

 

[CountMike]

Just to make it clear, secure erasing "empty" space and just clearing space are two different things. Backup is a must in any case.