Sensitive files remain on your hard drive after you delete them using File Explorer, and even after you empty the Recycle Bin. Anyone can recover your sensitive data using file recovery software. When you delete a file, only information about the location of the file on the hard drive is erased. To delete the data permanently, use a tool -- such as DeleteOnClick, File Shredder or CCleaner -- to overwrite it.
DeleteOnCLick adds a Securely Delete option to the context menu when you right-click a file. File Shredder can securely erase several files or folders at a time. CCleaner doesn't permanently delete individual files, but can overwrite the free space on partitions, making all deleted files unrecoverable.
Caution: Recovering overwritten data is impossible in most cases.
Open the OnClick Utilities Downloads, download the installer and save it on your hard drive. Double-click the installer to launch the setup wizard and then follow the instructions to install the utility.
You need around 2MB of free disk space to install DeleteOnClick. This utility adds a new option to the context menu when you right-click a file in File Explorer.
Open the folder that contains the file you want to permanently delete, right-click the file and select Securely Delete from the context menu.
Click Yes to delete the file permanently. The file is overwritten in three passes. DeleteOnClick overwrites the sensitive information three times using random data and different overwriting algorithms, making data recovery impossible. The process may take more than one minute for files over 500MB.
Open the File Shredder 2.5 page, click Download File Shredder and save the file on the hard drive. Double-click the installer and follow the instructions to install the utility.
Launch File Shredder and click the Add File(s) or Add Folder if you wish to permanently delete an entire folder.
Select the file you wish to permanently delete and then click the Open button to add it to the queue in File Shredder. You can select several files by holding Ctrl and clicking each item. To select all files in the folder, press Ctrl-A.
To remove some of the files from the queue, select them and then click Remove Selected in the left pane. To remove everything from the queue, click Remove All.
Click the Shred Files Now button to permanently delete all files in the queue. Click OK to confirm, if you are sure you wish to permanently erase the data. The process takes less than a minute for small files, but can take up to five minutes for large amounts of data.
In time, Windows writes new files over deleted ones -- which still exist on the drive, but are invisible. Shredding free space overwrites all these invisible files on the entire partition -- or entire hard drive -- immediately, making them unrecoverable. To shred free space in File Shredder, click Shred Free Disk Space in the left pane, select a drive and then click Next.
To change the number of passes, select a different algorithm from the Select Secure Algorithm box. One or two passes is usually enough for most people; the overwrite process takes a few minutes. The DoD 5220-22.M algorithm overwrites the data in three passes; three passes provide a good balance between time and security. The seven-passes algorithm and the Guttman algorithm (35 passes) are more secure, but overwriting the data takes significantly longer.
Open the CCleaner 5.0 page, click Free Download and save the installer on your computer. Double-click the file to launch the setup wizard and follow the instructions to install CCleaner.
Launch the utility, select the Options tab and then select the Settings tab.
Click the Secure file deletion radio button and then select the type of overwrite from the drop-down box. One pass or three passes (United States Department of Defense standard) provide a good balance between security and time. Seven passes provide more security, but the overwrite process takes longer. Wiping the free space using the Guttman algorithm (35 passes) takes significantly longer while the increase in security is relatively small.
Select the drives to wipe from the Wipe Free Space Drives section. To also overwrite the Master File Table, check the Wipe MFT Free Space box. The Master File Table stores all file information -- file size, the date and time it was created, user permissions and even information about file content.
Select the Cleaner tab in the left pane and then check the Wipe Free Space box. Click OK to confirm.
Change any of the other options before running the cleaner and then click the Run Cleaner button to wipe the free disk space from the partitions you selected in the Wipe Free Space Drives section. Wiping the free space makes all previously deleted files unrecoverable.
Tips & Warnings
- Wiping utilities overwrite your data with ones, zeros or random data in several passes during the wiping process. Three or seven passes are enough to make data impossible to recover.
- The Gutmann algorithm -- used by File Shredder and CCleaner -- overwrites the data in 35 passes. At the time of writing, no software can recover data overwritten using the Gutmann algorithm. In fact, even recovering data overwritten in three or seven passes is almost impossible.
- The United States Department of Defense standard for wiping hard disk drives -- DoD 5220.22-M -- overwrites the data in three passes.
- Overwriting the data makes it unrecoverable. The files can't be recovered by any software or data recovery professional.