Deleting Your Information

Technically, there is no delete function on your computer. You might be familiar with the process of deleting a file, which means dragging a file to the Recycle Bin. To be extra cautious you may empty the bin afterwards. However, all this does is clear the icon of the file from your desktop and tell your computer the space can be used for another file. You should also keep in mind that files are created and insecurely deleted, without your knowledge, every time you use your computer.

Remember, too, that computer hard drives are not the only devices that store digital information. CDs, DVDs, USB memory sticks, floppy disks, flash memory cards from mobile phones and removable hard drives all have the same issues, and you should not trust a simple delete or rewrite operation to clear sensitive information from any of them.

There are numerous ways by which you can delete your information. Using a tool to help you securely remove files means that you are replacing, or overwriting your information rather than just deleting it. This will ensure that rather than just visibly removing a file from your folders, the information does not remain in storage. The way the software does that is by overwriting files with random data several times. This process is called wiping, and the more times information is overwritten, the more difficult it becomes for someone to recover the original content. Experts generally agree that three or more overwriting passes should be made; some standards recommend seven or more. Wiping software automatically makes a reasonable number of passes, but you can change that number if you like.


Wiping Files

There are two common ways to wipe sensitive data from your hard drive or storage device. You can wipe a single file or you can wipe _all of the 'unallocated' space on the drive. [_Eraser](https:\/\/securityinabox.org\/en\/glossary#Eraser) is a free and open-source secure deletion tool that is extremely easy to use. You can wipe files with Eraser in three different ways: by selecting a single file, by selecting the contents of the Recycle Bin, or by wiping all unallocated space on the drive. Eraser can also wipe _the contents of the Windows [_swap file](https:\/\/securityinabox.org\/en\/glossary#Swap_file), which is discussed further below.

Beware:

While secure deletion tools will not damage any visible files unless you explicitly wipe them, it is still important to be careful with software like this. After all, accidents happen, which is why people find Recycle Bins and data recovery tools so useful. If you get accustomed to wiping your data every time you delete something, you may find yourself with no way to recover from a simple mistake.

Removing Temporary Data

Eraser can not help you clean up sensitive information that has not been deleted, but that may be extremely well-hidden. Files containing such data may be tucked away in obscure folders, for example, or stored with meaningless filenames. This is not a major issue for electronic documents, but can be very important for information that is collected automatically whenever you use your computer.

Examples include:

  • Temporary data recorded by your browser while displaying web pages, including text, images, cookies, account information, personal data used to complete online forms and the history of which websites you have visited.
  • Temporary files saved by various applications in order to help you recover work, should your computer crash before you can save. These files might contain text, images, spreadsheet data and the names of other files, along with other potentially sensitive information.
  • Files and links stored by Windows for the sake of convenience, such as shortcuts to applications you have used recently, obvious links to folders that you might prefer to keep hidden and, of course, the contents of your Recycle Bin should you forget to empty it.
  • The Windows swap file. When your computer's memory is full, for example when you have been running several programs at the same time on an older computer, Windows will sometimes copy the data you are using into a single large file called the ‘swap file. As a result, this file can contain almost anything, including webpages, document content, passwords or encryption keys. Even when you shutdown your computer, the swap file is not removed, so you must wipe it manually.

In order to remove common temporary files from your computer, you can use a freeware tool called CCleaner, which was designed to clean up after software like Internet Explorer, Mozilla Firefox and Microsoft Office applications (all of which are known to expose potentially sensitive information), as well as cleaning Windows itself. CCleaner has the ability to delete files securely, which saves you from having to wipe unallocated drive space, using Eraser, after each time you run it. BleachBit is another free tool that thoroughly cleans your PC and shreds files to prevent data recovery.

Make secure file deletion a habit

You are now familiar with a few of the ways in which information might be exposed on your computer or storage device, even if you are diligent about erasing sensitive files. You also know what tools you can use to wipe that information permanently. There are a few simple steps that you should follow, especially if it is your first time using these tools, in order to ensure that your drive is cleaned safely and effectively:

  • Create an encrypted backup of your important files as discussed in our guide. See How to recover from information loss.
  • Close down all unnecessary programs and disconnect from the Internet.
  • Delete all unnecessary files, from all storage devices, and empty the Recycle Bin
  • Wipe temporary files using CCleaner.
  • Wipe the Windows swap file using Eraser.
  • Wipe all of the free space on your computer and other storage devices using Eraser. You might need to let this procedure run overnight, as it can be quite slow.

Hard Drive/Permanent Deletion

If you need to destroy all the files on your computer, make sure to backup and encrypt what you are permanently erasing to an external hard drive or a secure cloud based service.

See How to securely erase your hard drive

What you can use to erase your hard drive:


Sources


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