Most people, especially those who are not technically minded, consider a data file to be deleted when the Delete button is pressed on a computer system.
In most cases, data deleted by normal methods can be easily recovered, depending on how exactly the data in question has been erased.
There are typically three ways that data can be deleted from a computer system, these are as follows:
- Delete to Recycle Bin (Windows operating systems only)
- ‘Permanent deletion’
- Secure erasure by overwriting data
Deleting data by using the first method does not actually delete files at all, it just moves them to a different part of a hard disk, in a folder called the Recycle Bin. These files can be restored by going into the Recycle Bin, right-clicking on the relevant file, and choosing the Restore File option.
Files that have been ‘permanently deleted’ are actually just marked as deleted by the operating system, with the space that the file occupies being marked as available for use by other files.
This means that files deleted in this fashion are actually still there until overwritten by the operating system. To recover these files, you need to use a data recovery software program.
It is vital that this program is ran from a different device to the one that you are recovering lost data from, i.e. a software solution could run from a USB device or CD-ROM drive.
Also, in order to prevent data corruption on the device being analysed, it is equally important that any files recovered are saved to a different device as well.
Most data recovery programs have different options for recovering data, which means that in some cases you may need to manually select the most thorough scanning mode in order to get your files back. In most programs of this type, this mode is usually labelled as Deep Scan.
Files that have been deleted by secure erasure, which is where the data is overwritten in addition to files being marked as deleted, cannot usually be recovered. This is unless any automated backup copies of files exist within the device.
An example of such backups are sometimes taken automatically by the System Restore application (on Windows operating systems), if the computer in question has this setting enabled.
Such backups can also be created by the automatic file save feature in Microsoft Office. This only applies to files created using this application, however, for those files, this can be invaluable when it comes to recovering lost data.
By default, applications within this suite of programs save recovery backups every 10 minutes or so, meaning that at the most, users would lose a minimal amount of work should they encounter a system failure.
If such a document is accidentally deleted, it can sometimes be recovered by opening the relevant application and following the on-screen prompts. This is possible because when an automatic recovery file exists, the relevant application detects and prompts the user automatically.
Data recovery using specialist hardware can sometimes recover a few bytes of information, however it is rare to be able to recover enough information to be able to reconstruct a file, as hardware recovery can only normally get a few bytes of data back at the most.