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