Getting Rid of Hard Drives (Safely)

In an effort to reduce clutter at home, we’re trying to get rid of things that we no longer need, or don’t want anymore. For many types of things, this isn’t a problem — box it up and fire it off to Goodwill, the library, e-waste, or other charities. However, certain types of junk require special care to avoid trouble.

As a bit of a pack rat, I tend to keep around old computer hardware, under the catch-all reasoning of “I might want to put another machine together!” This collection includes old hard drives, which naturally contain lots of my personal information thanks to their day-to-day usage in a personal computer. Getting rid of this information securely involves using a secure deletion program (such as SDelete, Eraser, or DBAN). These programs overwrite files and free space with a number of different patterns, to ensure that the data cannot be recovered easily, if at all.

(I also wound up using a partition editor program to reformat a drive’s partitions as NTFS — it used to contain a Linux distro. After the NTFS reformat, I then wiped all the free space on the hard drive, thereby achieving the same effect as securely deleting it in its original format.)

Techniques for overwriting data, and recovering data using specialized hardware, are described in this paper. Interestingly, it is practically impossible to completely remove all traces of magnetic reads/writes due to the lack of drive head positioning consistency in hard drives. However, modern advances in hard drive platter density apparently make the data recovery techniques in the article unfeasible for a reasonable number of random overwrites. (Of course, for top secret information, the sanitizing method of choice is still physical destruction of the drive.)

Overwriting entire hard drives, I have discovered, is extremely slow. Because of the need to use uncached disk access, wiping a 100+ GB drive (5400 RPM if I recall correctly) can take more than a day. However, it’s definitely worth it — there are quite a few articles out there describing data recovery efforts on hard drives acquired from swap meets, eBay, and so on, and the ease with which sensitive information is acquired is certainly a bit alarming. By taking these extra steps to sanitize my old hard drives before I get rid of them, I’ll avoid any unpleasant surprises down the road.

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