SECURE DATA          ERASURE:          PREVENTING          UNDELETION

As you may know, when files are deleted, they aren’t truly gone. Even after you empty them from the Recycle Bin, there are ways to retrieve that “deleted” data using software easy enough for a novice to use. Data recovery professionals in a clean lab can have even greater chances of recovering deleted data. Much of the content on this website deals with undeleting files and recovering lost data. But what if you wanted to make sure that your data can’t be undeleted? There are a few ways to securely wipe your sensitive information from a hard disk drive, memory card or solid-state drive. Read on to learn the pros and cons of each.

SECURE FORMAT AND SECURE DELETE When a file is deleted, it is removed from the file system but remains written on the physical drive until something overwrites it. The concept behind secure deletion and secure formatting is that it proactively overwrites the sectors with new data or zeros to ensure that all traces of the data are eradicated. A secure delete attempts to do this only on the sectors where the data resided. A secure format wipes the entire disk or drive and overwrites every available sector. Because a secure delete may not account for cached, temporary or other residual files on the disk, a secure format is the safer option. Another disadvantage that applies to both secure formats and secure deletion is that some disks will not overwrite sectors that have been marked as bad sectors. When bad sectors are detected on a drive, the firmware will stop using it. There aren’t usually ways to override this from a normal operating system. Also, a recent study at University of California San Diego found that most secure erase methods don’t work on solid state drives.

DEGAUSSING Data is written to hard disk drives magnetically. When a drive is degaussed, it is placed into a moving magnetic field and the data is effectively scrambled, and therefore unreadable. After degaussing, the disk will usually be unusable. This is a slight disadvantage, since it cannot be mounted in order to verify that the data was successfully removed. Also, solid state drives are not magnetic and cannot be degaussed.

PHYSICAL DESTRUCTION Disks can also be physically destroyed by drilling a hole through them. However, a determined technician could still recover data from the remaining intact portions of the drive. To prevent this, there are some companies that offer hard drive shredding that grind the drive into tiny pieces. Shredding a disk, memory card or drive is the most secure disposal method. While a low level / secure format and/or degaussing is sufficient to deter most would be data thieves, in theory, the data could be retrieved. If you are trying to bar everyday computer users from undeleting moderately sensitive information (such as browser history, old Word documents and photos), a secure format or secure deletion software will usually do the trick. But if you are attempting to safeguard confidential data or company secrets, go with a hard drive shredding service.

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