Secure Delete to Erase Confidential Files
If you want to permanently delete confidential files from your hard drive, be sure that you follow a procedure for a secure delete. With a normal file delete, the data in the file is not erased. The disk space previously occupied by the file becomes available as free space for use, but it is not erased or overwritten until that free space on the hard drive is used to store another file.
Even if you re-format the hard drive, the old data is not erased. Don’t assume that if you want to sell or donate an old computer, you can just delete your files or re-format the drive. There is data recovery software available that could read your old data.
Secure Delete on Hard Drive
To permanently delete files on a hard drive, you need to overwrite the old files with a useless data pattern. To eliminate residual magnetism that could be used to recover the original data, overwriting the old data 3 or more times provides more security. Overwriting is also known as sanitizing, wiping or file shredding.
DOD 5220.22-M Data Sanitization
You can use a software utility program that follows the Department of Defense (DOD) 5220.22-M procedure to sanitize magnetic files on a hard disk. It is one of the most common sanitization methods used in data destruction software.
The DOD 5220.22-M data sanitization method is usually implemented in the following way:
- Pass 1: Writes a zero and verifies the write
- Pass 2: Writes a one and verifies the write
- Pass 3: Writes a random character and verifies the write
File Shredder Software
On my Windows PC, I have several programs that include a secure delete tool. It is included in the toolbox section of Advanced System Care (ASC) as IObit File Shredder. You can use it to delete files, a folder or the recycle bin.
Glary Utilities includes a File Shredder and a Wipe Free Space choice in the advanced tools section. Some other software choices are Darik’s Boot And Nuke (DBAN), and Eraser. Similar programs are available for MAC and Linux systems.
For additional security, you can store files using encryption software such as TrueCrypt.
Be sure that when you want to permanently delete a confidential file, or dispose of an old computer, you use secure delete. If you have already deleted some files without secure delete, you can use a wipe free space utility to overwrite those files.