| When you delete a file from your computer, it | | | | What this means is that no recognizable |
| may seem permanent and irreversible enough, | | | | traces of the shredded file remains on the |
| but in fact it isn't. It is still possible to | | | | hard disk after deletion. |
| recover this data through a variety of means, | | | | |
| using software designed for this purpose. | | | | This can be better understood by realizing |
| This may be helpful for accidental deletions, | | | | that the data contained within any type of |
| but when private or confidential data is | | | | file can be reduced, fundamentally, to some |
| involved, this represents security | | | | series of 1's and 0's that then form bits and |
| vulnerability. | | | | bytes. Ordinary file deletion leaves the |
| | | | majority of this sequence of bits unchanged, |
| File deletion works by just changing the tag | | | | changing only the small portion of it |
| on a particular file to the value 'deleted', | | | | corresponding to the "deleted" or "available" |
| and making it inaccessible from the default | | | | metatag. File shredders, on the other hand, |
| set of menus and directories. However, the | | | | overwrite these bits with random bits, |
| data and the file itself actually remain on | | | | effectively masking the old pattern that was |
| the hard disk, and only disappear when it is | | | | contained in the shredded file. |
| overwritten in the future by new data. But | | | | |
| this overwriting may not happen until after | | | | Because nearly all traces of the original |
| the file data has already been recovered! | | | | data are wiped clean, it becomes next to |
| | | | impossible to retrieve any useful information |
| In fact, some operating systems have a | | | | from files shredded in this manner. Many file |
| built-in UNDELETE command, which can easily | | | | shredders perform this random overwriting |
| recover recently deleted files. Hence, this | | | | process several times to ensure that the |
| really is a big vulnerability that can be | | | | resultant pattern is truly random, and is no |
| exploited by malicious parties to gain access | | | | longer correlated with the old data. |
| to confidential or private information. | | | | |
| | | | These file shredders can sometimes also deal |
| An analogous problem arises in disposing of | | | | with entire hard disks at once. This is |
| confidential paperwork, and the typical | | | | useful when disposing of or transferring old |
| solution is to use so called paper shredders. | | | | computers, for instance, to ensure that no |
| These shredders tear the paper into fine | | | | recoverable data remains on the hard disk. |
| strips which are then nearly impossible to | | | | These hard disk wipes work on the same basic |
| reconstruct the original from. The solution | | | | principle as shredding an individual file: |
| to the digital counterpart of the problem | | | | all of the data on the hard disk is |
| lies in software, also called shredders. | | | | overwritten with random bits. |
| | | | |
| These utilities are known as file shredders | | | | Many file shredders (super shredder, for |
| (examples include Super Shredder, among | | | | instance, but there are others) are available |
| others), and are designed to permanently | | | | for download or purchase on the internet. |
| delete any particular file or group of files. | | | | This means that secure deletion is easier |
| This is done by overwriting the actual data | | | | than ever to perform. |
| in the file to be deleted with random data. | | | | |