So today, I finally retired my old work laptop. As I’m a relatively security-conscious person when it comes to my old hard disks, I thought I’d share what I did.
First off: Even if you “delete” all the information on your hard disk, it’s still there. Yep. A format doesn’t get rid of it, and it’s possible to extract that old data. There’s only one way to permanently delete so that it is unrecoverable without physically destroying the disk: use a utility which overwrites the data with something else.
But just one time won’t do it. You have to overwrite it a bunch of times, because the old data still lurks as a magnetic “shadow” of its former self, right there on the disk underneath the data.
Enter “shred”. You can boot from any Linux Live CD (Gentoo, Ubuntu, and SuSE all have one), and there will be a little utility called “shred”. You will probably have to download and burn an ISO image first to get a copy of Linux.
Once you have the CD burned, boot to it, and type the following commands at a terminal window (The “$” and “#” indicate a prompt, you don’t type that):
$ sudo bash # shred -vfs /dev/hda
This will take a few hours, but once it’s done, you can rest assured that your old data is unrecoverable by all but the most expensive and time-consuming recovery methods, and then, it will probably be only a partial recovery, if any. Your hard drive will be safe to sell on eBay or whatever.
Now, if you want to be really pedantic, rather than overwriting the default 26 times (25 times with random data, 1 time with zeroes at the end), change the flags to “shred”:
# shred -vfs -n 100 /dev/hda
This would erase the data 101 times in a row (100x with random noise, 1 time with zeroes for a final pass). It may take a weekend to complete, but that hard drive will be clean and ready to get rid of without compromising your personal information.
As the coup de grace, of course, on this hard drive I have in the laptop before me which is being shipped back for destruction, I will install Ubuntu Linux. Just to remind whoever gets the machine that I am, after all, a budding Linux guru. Fear me.
People Don’t Realize
We had a guy in the next county who gave his brother his old computer, who then sold it to a pawn shop, which looked at the drive and saw some child pornography on the hard drive including pictures with the ORIGINAL OWNER IN THEM.
So please take down these instructions so those kinds of idiots do not know how to cover their tracks.
My $.02 Weed
Because tech is abused by
Because tech is abused by some does not mean it should not be used. People need to stop committing the acts. Don’t blame the computer. That’s like saying you should always be handcuffed in public because the only use for your hands is crime.
If I were to take it down…
If I were to take it down, that would mean that I’m also depriving fully legitimate people of the opportunity to keep their data safe. Tons of programs store passwords all over the hard drive… this, in particular, is why I shredded it. I have a zillion emails, and users routinely send me their passwords in these emails. They’re not supposed to, but they do anyway.
So if I were to not do this myself, I could potentially endanger the data of hundreds of other people who have trusted me with their account information. It’s better that everybody, everywhere follow good data security practices.
I hate the abuse engendered by child pornography as much as the next guy, but the smart and educated ones avoid prison anyway because they already know this stuff. You tend to catch the stupid ones.
This topic actually dovetails nicely with my next blog entry, due to come out tonight…
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Matthew P. Barnson
Uhm Dude
Didn’t really mean for you to take down the instructions. It was more of a “look at this idiot” post.
Sorry for the misunderstanding.
My $.02 Weed
I missed….
See, that’s the problem with Internet communication. You miss the sarcasm and irony which show through when someone’s actually talking…
—
Matthew P. Barnson
Data Elimination suggestion
Here is another take on how to ensure that your data is eliminated from your HD.
🙂
That’s literal!
Boy, they’re really literal about it…
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Matthew P. Barnson