Published 20.04.2009 ‘Gadget Speak’ Engineering & Technology Magazine
“Manuscripts do not burn” proclaimed the devil in Mikhail Bulgakov’s epic tale ‘Master & Margarita’. Well, digital storage devices definitely do, if that’s the solution you favour for retiring old media. There are other ways, however, to effectively delete unwanted data, sanitise hard drives and flash media storage devices.
As previously mentioned in the Trade Secrets column (March 17, 2009) – deleted or corrupted images on digital cameras can be restored. Computers and digital media devices cannot erase data. The delete command only modifies the relevant file descriptors in the operating system and previously assigned disk space is marked available for overwrite. The icon disappears from screen but the content is still there. Formatting has a more or less similar effect. This holds true for most personal computers, PDAs, digital cameras and flash memory.
Aside from degaussing, burning, microwaving or ingesting your digital storage device, there is only one sure method of deleting unwanted data whilst preserving use of the device itself. Every addressable block occupied by the original files needs to be overwritten with ASCII NUL bytes (zeroes). Experts recommend using several different patterns (or passes). For example, the US Department of Defence enforces three to seven passes, depending on the document’s sensitivity, when requiring its permanent and secure deletion (also referred to as wiping).
Today’s software options have made this process incredibly easy. Eraser for Windows and Permanent Eraser for the Mac OS X are free tools that can wipe files and entire disk drives using the specified number of passes. Eraser can also wipe all remnants of past files stored in the empty space of your hard drive or media device. This feature is known as a free space wipe. On the Mac OS 10.4 and higher it can be achieved from the Disk Utility function by selecting Erase and then the Free Space button.
Don’t forget to delete the temporary files on your computer, collected whilst browsing the Internet, working with documents and media. Ccleaner for Windows and Onyx for MAC OS/X can locate and delete them for good.
Once all necessary software is installed, run a free space wipe, followed by a clean up of your temporary files. From now on, use wiping tools to delete unnecessary data and don’t think twice about sharing your PC again!