If you have decided to sell your old computer or donate your computer to colleges or schools, you need to make sure that all the personal data inside your computer hard disk is deleted. Deleting your data from hard disk only removes the data from the file system, but the data is still physically present in your hard disk. Simple data recovery software can easily recover the entire data from the hard disk.
How deleted data are recovered?
A simple delete/quick format of hard disk removes data only from the file system therefore hiding the data from the user. But actually the data is present physically in the hard disk until the data is overwritten. Data recovery software can easily recover this data from the hard disk, if required.
How does the sanitization programs work?
These special programs will write some random data (mostly 0’s and 1’s) in the hard disk, overwriting every single bit of data present in the disk. Since all the data present in the hard disk is overwritten, it is next to impossible to recover the data from the hard disk.
Most of these programs uses single pass, which means it will overwrite the entire data on the disk once. There are multiple pass programs like (DoD 5220.22-M, Gutmann Method) which overwrite the data more than once to ensure the data is gone forever.
Fact: ‘Gutmann data Sanitation Method’ used on the WikiLeaks Server when it came up for sale on Ebay. Gutmann method overwrites random data 35 times in the hard disk which prevents all the possibilities to recover any data from the drive.
How to delete the data permanently from the hard disk
The data can be deleted permanently by
- Windows Format (Windows Vista or higher)
- Some special software like DBAN (Darik’s Boot and Nuke) available which deletes the data permanently from hard disk. The good thing about this software is it’s FREE.
- Physically destroying the hard disk
Windows Format is usually the easiest method to permanently delete data from hard drive. Just insert the hard disk, right click on the drive and give format. It’s done. Just make sure to uncheck the Quick Format so that all your data in the hard disk is overwritten by some random data.
Note: Starting from Windows Vista, Windows gained the power of writing zero’s in the hard disk whenever it is formatted. Lower version of Windows does not have this capability. If you are using Windows XP, or lower check on the using other software like DBAN to wipe off the data.
But if you want to format a partition where windows installed the above method is not possible. In this case you need to boot to Command Prompt using System Repair disc and issue Format Command from Command Prompt.
Check on how to boot into Command Prompt to boot from System Repair disc. Once booted using the System Repair Disc, just follow the instructions to Format Hard disk.
DBAN (Darik’s Boot and Nuke)
DBAN is the best software available for completely erasing the data from the hard disk. This method overwrites the hard disk with the random values so that the data recovery is extremely difficult (Almost impossible). This is the best option available till now, loved and used by many of the computer geeks.
Steps to permanently delete the files using DBAN
- Download DBAN.
- Once downloaded, burn the .iso file into CD or DVD.
- Boot your computer using this CD/DVD. Check on How to boot using CD/DVD for steps to boot from CD or DVD.
- Follow the instructions shown in the screen to wipe the entire hard disk.
- Depending upon the method and the size of the hard disk, this process can take hours or even days.
Physically Destroying the Hard drive
If you want to be absolutely sure or don’t have time to wait for the sanitization methods to clear the data, then its better to physically destroy the hard disk.
The main idea of this is to destroy the inner platter of the hard drive where the data is stored. There are several methods to physically destroy a hard drive, burning, soaking in acid, whacking with hammer, drilling holes, hitting nails etc.,
Putting the hard drive in fire or soaking it in hydrochloric acid, you might run into hazard of releasing the toxin gases into environment or inhaling it.
I’m a lover of brute force methods, which involves simply whacking the hard drive with a hammer or drilling 5 -6 holes through it. Whacking the drive or drilling holes through the drives will make sure that the inner platter is destroyed.