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by Archives September 14, 2005

In an earlier column I mentioned that deleting a file doesn’t actually mean it’s gone. It’s like tearing the table of contents out of a book; you might not know where anything specific is, but you can still flip through the book and read as you please. This is what file recovery programs do and incidentally why identity theft is one of the fastest growing crimes in North America. People throw away hard drives full of personal information and identity thieves are only too happy to pore over them.

To understand how to destroy data, you need to know a little bit about how data is stored. The device responsible for data storage in your computer is the hard drive. The actual data is stored on hard drive platters, which are metal or plastic discs in the hard drive. Hard drives store information in binary code, by polarizing specific areas on the platter to represent 1s and 0s, like the way a floppy disk works. The hard drive can later interpret the polarization of that specific area as a 1 or a 0.

Probably the most convenient method of data destruction is to use any number of programs, that instead of just conventionally deleting the data, write over it several times. Each time the data is written over is called a ‘pass’, the more passes the harder it is to recover the data. Most software supports up to 35 passes, but the US Department of Defence recommends only 7 passes even for its more sensitive data.

Physical destruction of the hard drive is a reliable method of destroying data. What you’re looking for inside a hard drive are the platters, shiny silver or orange discs. Destroying the surface with a grinder or just shattering it with a hammer will do the trick. My personal favourite is playing ‘Ultimate Frisbee’, also known as throwing them at my roommate when he’s not looking. Hard drive shredders are supposed to be very effective. Think wood chipper, but for metal, except they aren’t available for personal use. Melting the drive down would be perfect, but sadly I only know two people with smelters in their backyards.

Alternatively, you could just heat up the hard drive to the platters’ Curie Point. The Curie Point of a metal is the temperature at which it loses it’s magnetization. The metal used to store data on hard drive platters is called ferrite, and it has a Curie Point of between 300-600

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