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Please mind that I'm a dilettante and tyro about computering and Ccleaner (tendered here).

The official https://www.piriform.com/docs/ccleaner/ccleaner-settings/changing-ccleaner-settings, says nothing about the permanent effects:

Select Secure file deletion (Slower) to delete files more securely, but much more slowly.

CCleaner has four methods of secure deletion: a Simple Overwrite (1 pass), DOD 5220.22-M (3 passes), NSA (7 passes), and Gutmann (35 passes). A 'pass' refers to how many times CCleaner writes over the spot on the hard drive. The more times CCleaner writes to that spot, the harder the file will be to recover by any means. The drawback is that it will take CCleaner longer to complete the job.

Yet http://forum.piriform.com/index.php?showtopic=33032&p=196885 alleges:

35 or really anything over 1 secure, is overkill a will DRASTICALLY reduce the lifespan of your drive

Is this true? If so, what's the optimal number of passes? Are there any other effects?

Supplementary: I don't know the type of disk drive, so I accessed Device Manager which lists, under 'Disk Drives', 'Hitachi HTS 547 575 A9E3 84' (The spacing here is my own, to facilitate reading).

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https://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html worth a read if you want to understand why 35 passes exactly. Epilogue if you want to know why its overkill.

In short, the "35 passes" assumed older encoding techniques and lower data densities. It also assumed you had no idea how the drive was encoded. Each pass used a method specific to a drive type in use in the 90s, and even then, one appropriate pass was good enough. With modern drives, there's just so much data, that anything you missed would be lost in a sea of garbage.

In general one pass, and a check with a good reliable recovery software would be enough.

If you're deleting individual files, you may not have direct access to the parts of the hdd that you're using, and the best way is to cause the files to be overwritten indirectly (sdelete's docs describes this process). I suspect cccleaner uses a similar approach. Even then a single pass with random data should be enough, and you can probably do a quick check to ensure the files arn't trivially recoverable.

A 3 pass (HIPPA), 7 pass (DOD) and 35 pass Guttmann wipe is primarily useful when needing to check boxes off on a checklist and nothing more. I'd note unless you're obsessively clearing your drive like Lady Macbeth washes her hands in the Scottish play, you're unlikely to do any significant amounts of writes to your hard drive compared to lifetime usage. You'd be better off encrypting in that case.

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