Sometimes, it is important to delete data. This can range from sensitive documents to keyfiles. The ability to erase securely is more important when using public computers, or shared computers. Also, if you are selling away old hard disks, it is very important to securely format such drives. There have been many cases of data thefts recovering sensitive materials from hard drives sold off in auctions. Deleting the data from the recycle bin is not enough, or using shift+delete does not really delete the data. What these operations do is remove the index of the particular files from the index. A file recovery tool, as demonstrated above, can recover files from such drives. The data will remain in the hard drive for long periods of time, especially if the files are small in size.
Software for securely deleting data are available. These software delete the file from the index, as well as replace the actual data on the drive with pseudorandom data. The physical location of the data on the disk is overwritten, so the chances of recovering the data is greatly reduced. We will be showing how to use two free programs for deleting data, but there are more available. These are both freeware. FreeCommander is an alternative to Windows Explorer, and has a number of extra features. FreeCommander securely deletes data quickly and easily. Eraser is another application, and it can be configured to overwrite the data many times over. Eraser is the more secure and robust file shredding application, but is also far more time consuming because of the numerous overwrite runs required. Free Commander is a free file browser that makes exploring the file system easier. Folders show up with sizes, and there is a dual pane interface that makes moving data around a breeze. To securely delete data, select the files or folders, then go to File>Wipe.
Free Commander offers upto 10 overwrite runs. Each “run” involves rewriting the area where the data was stored with random data. The more the runs, the more irrecoverable the data becomes. However, if you have deleted data, without wiping it, then it can be recoverable by a file recovery software.
Free Commander has no function to erase the empty hard disk space, and rewrite the empty information. This is where Eraser steps in. Eraser is a deceptively simple looking program. Eraser can securely delete the data even in the free space section of the hard drive, where data exists, but is not indexed. Go to File and add tasks to add the parts of the hard disk that has to be erased. The user can add empty hard disk space, specific folders, or individual files. Each operation is called a task, and any number of tasks can be added to a list known as the task list. Eraser goes through the task list, erasing the identified data one at a time.
At each instance of an erasing operation, there are a whole range of secure deletion options available to the user. There are a few default patterns in which the erasing occurs, but this can be entirely tweaked by the user. The most secure default pattern offered by the program is the Gatmunn method, which involves thirty five passes.
This is more than anyone really requires. However, to give yourself the illusion of extra security, and more importantly, peace of mind, you can choose to create your own erase/ overwrite patterns. Click on new to create your own pattern. You can specify an unlimited number of passes, and define what kind of data is used to overwrite the file or empty space in each of these passes. A pattern overwrite uses a specified pattern, and the pseudorandom data overwrites with random characters. We specified an operation which implements 101 passes.
Note here, that the more passes you specify, the more is the time taken. Overwriting files and folders is a relatively fast operation, compared to rewriting all the empty space in a hard disk. Even a 10 passes operation will take a long time when it comes to clearing hard disks with a lot of empty space. Also note that two or more identical passes, following the same pattern (say all zeroes) is the same as one pass with that pattern. Either alternate the pattern, or sandwich patterns between two pseudorandom data passes. Deleting all the existing data in the hard drive, then erasing all the empty space using Eraser will securely delete all the data on your hard drive. Now even specialists cannot recover the data easily from your hard disk. It is safe to sell or dispose hard disks only after you have securely deleted all the data on the drive.