Thread: Securely deleting data

Ideally, you should be using public computers like a ghost. No trace of your activities on the computer should be left behind. If you have downloaded any kind of data, or have created data in the cybercafe, it is a good idea to delete the data before you leave. Even if you use [Shift] + [Delete) to get rid of the data, or empty the Recycle Bin, the data is still there on the hard drives, but not indexed in the filesystem. This means that fairly simple and commonly available file recovery software can be used to recover the deleted data. There are a number of free and portable programs to securely delete data from the hard drive. These programs manage to do this by overwriting the empty space, or the areas of the hard disk occupied by the file. We will be using two programs for securely deleting data-Free Commander and Eraser. Free Commander is faster, less secure, but should do for most day to day purposes. Eraser is a highly-specialized application, and can offer as much security as time permits.

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 ten 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. 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. 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.