I had some drives that were defective and needed to be RMA'ed. I was concerned about sending back a bad drive with critical corporate data that may still be recoverable. Since I could not wipe the drive with software because the OS would not recognize the drive, I looked into buying a degaussing bulk eraser but found out they cost about ten times the cost of a new drive.
I got the idea of using a permanent magnet to erase the drive but I read many postings of people who tried but failed using old speaker magnets. I then found a site called K&J Magnetics (http://www.kjmagnetics.com/) which sells super strong neodymium rare earth magnets.
I did some experiments on an extra working drive. The neodymium magnets fully erased a hard drive with less then 30 sec of rubbing in circles on both sides of the drives. They also worked great to erase 3-1/2" floppy disks and some flash memory cards.
Just be carefully to read and heed the warnings about the magnets on K&J's site. The magnets are much stronger than you could imagine. Getting your finger caught between two magnets will cause a serious pinch. Also they are incredible hard to get apart once they stuck together.
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Nice tip, although I wouldn't suggest doing this to a drive that will remain in use. Even a slight bend on the read/write heads or a misalignment of the spinning mechanism can put the tip of the heads straight onto the platter, and at 5000+ RPMs, you get the picture. Just don't do it on a good drive unless you can afford to make the gamble.
Running a magnet (even a super strong one) over the drive is no guarrantee that the data is unrecoverable. You have no way of knowing if the data was wiped or just a few bits of the allocation table got corrupted. Professional data recovery can sometimes get data from a drive that has been written over several times.
If it is "critical corporate data" as you say, you just eat the cost and throw the bad drive in the incinerator. Why risk $millions in lawsuits, intellectual property loss, and bad press for stupidity over a $200 hard drive.
Discarding and RAM'ing a drive are apples an oranges when you think about what is involved in the support contract. Dell would not be happy if they got back a hdd that look like it came off airplane wreck. It defeats the point to getting a 'free' replacement. Our best practice these days is to only use bonded couriers to return the drives, data gets out, law is on our side.
1. This isn't enough: at least 50% of the data can still be recovered when erased with a permanent magnet, it doesn't matter how strong it is.
2. Magnetic fields have absolutely nothing to do with Flash memories: your memory was already damaged or files already corrupted.