How do I securely delete my files?

If you’ve purchased the bonus software edition of this magazine then you can use your unique code to download and register a complete copy of O&O SafeErase 15 ( see p66). This tool can scan your hard disk for files that have been insecurely deleted, along with other items such as browser caches and temporary OS files, and overwrite them to ensure they can’t be recovered. It can also overwrite all the free space on a drive, to remove any remnants of long-deleted files, and wipe entire hard disks.

Six security levels are offered: the lowest levels overwrite the relevant disk areas with zeros or random bits, while higher settings enable three, six, seven or 35 passes. You’ll see an estimate of how long the process will take at each setting, so you can balance speed against thoroughness. A reminder, though, that large numbers of passes are unnecessary, and could shorten a drive’s working life.

The open-source solution

Another free, open-source option is a tool called Eraser, which you can download from eraser.heidi.ie. This adds two options to the right-click context menu in the Windows File Explorer: Erase immediately deletes and overwrites any file, while “Secure move” copies the file to a different location then wipes the original, so no trace of it remains on the original disk.

A total of 13 different security methods are supported, ranging from a single pass to, once again, a complete Gutmann process in 35 parts, and Eraser also has a scheduling engine that can periodically scan user-selected folders and overwrite any deleted data it finds. Another interesting feature is the ability to overwrite deleted data with copies of other files, so that if anyone examines your disk they’ll see ordinary data rather than the telltale bit patterns of a secure deletion algorithm.

The tool that’s built into Windows

If you’d prefer not to install extra software, you can use a command-line tool to ensure that deleted files can’t be recovered. It’s called cipher, because its primary function is to encrypt and decrypt files, but it also has the ability to find deleted data and overwrite it three times, using first zeros, then ones, then random numbers.

To run the tool on your Windows system drive, open a Command Prompt as Administrator and enter the following:

cipher /wc:\

The /w switch tells cipher to carry out an overwrite operation, and it’s immediately followed by the path you want to purge of deleted data. If you specify a folder – such as c:\users\darien\ documents – then only that folder (and any subfolders) will be scanned.

While it’s nice that this capability is built into Windows, it’s a small inconvenience that you have to delete files first, and then run cipher afterwards. For a one-stop solution, you can download a semi-official command-line tool called SDelete, which erases and overwrites files in one go; see pcpro.link/335sdelete for more details and a download link.