Century IT blog

When I delete files from my hard disk is it really deleted or can someone access it?

July 22nd, 2008

istock_000006308318smallWere you aware that when you delete files from your computer that the files are not really deleted and can be undeleted? Defragmenting your hard disk after deleting files or rebooting your computer will make no difference.


Some companies, when disposing of their IT assets don’t even bother erasing the contents of their computer or server hard disks, or ensuring their IT support company properly erases the contents.


There has been a lot of bad press recently about hard disks, computers and servers being sold on EBay, found in computer auctions or sold on from companies which recycle computers. This IT equipment has been found to still contain the previous owner’s data and the data is still readable by the new owners!

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Basically this occurs because when you delete a file from your computer, only the information which maps the location of the file on the hard disk is erased, the location of the file still exists and the file still exists. These files can be retrieved using a range of readily available software titles on the internet or from your local computer shop. Undelete or un-erase software programs basically search the hard disk for files which can be undeleted and restore the ‘bookmark’ or location information so the files can be accessed again.


When disposing of computers and servers, you should ensure that the hard disks are professionally wiped, this means that some specialist computer hardware or software is used to properly erase the contents of the hard disks. The contents are erased by writing a sequence of meaningless data to each area of the hard disk, often several times over, this is normally enough to stop the opportunists or even an experienced computer technician.  More intensive and a more complicated pattern of writes means the less likely a 3rd party will be able to see your data after you have disposed of the computers or servers.