Data Destruction Revisited
Lifehacker has a good post about deleting data from a hard drive. We’ve actually covered wiping hard drives using dban here before. The lifehacker article goes through total disk wipes using dban, but also highlights some good tools for deleting individual files plus I think it is always good to remind people how their data is stored and subsequently deleted.
First, if all you have done is simply delete a file (move it to your trash and empty your trash) that file is not actually gone. Your hard drive works in blocks, a file takes up so many blocks, and when you delete a file the operating system simply allows those blocks to be reused. So with a few simple tools most files can be recovered from a simple delete or format. This is very important to remember if you are reusing a hard drive (which I don’t recommend).
A fairly safe method of wiping an entire hard drive is to use dban to do a total disk wipe. This works well because it sets every block to 0 and than randomly rewrites data and back to 0 (0 meaning nothing is there or an empty block). It is a pretty safe bet that your data is sufficiently gone unless someone with a lot of resources and time is out to get your data. The average user isn’t going to recover anything from your drive. I use dban if I am going to reinstall an OS. I have actually had some problems when I use a simple format so if I am going to reinstall Windows or Linux I always wipe the drive with dban first (some people don’t share my view, but I swear to you that you will be happier if you take the time to do that).
Now what to do when you need to get rid of a hard drive, especially one you cannot wipe first. It is hard not to be a little worried when you read stories like this where they were able to recover data from Columbia (the space shuttle that burned up on reentry). If you can recover data from an almost completely destroyed disk what can I possibly do to prevent this from happening on mine. First, recovering data from the space shuttle was of great importance to find out exactly what went on, but it would hardly pay off for the data on your disks. then there is the tid bit of how much time, energy, and money it would take to reconstruct an hd of such little significance (so unless you are storing state secrets or something you should be safe). Still it is probably a good idea not to make it easy on anyone. Shooting your drive with a shotgun should do a sufficient job to deter most, or drilling a few holes in the drive. Of course you can also do the credit card method (by which I mean cut it up into small pieces and throw the remains away in random containers).
Generally I say be smart, most of the stories you hear are from people who didn’t do anything to protect their data. If you take precaution than your data will be safe. I don’t think that there are too many people combing trash for used hard drives so they can mine useless pictures of your dog from the drive.