"Delete" does not mean "Erase"
Today more and more people have sensitive information that they would like to protect from falling into the wrong hands. If your hard disk contains valuable corporate trade secrets, business plans, personal files or confidential letters, you must know that the delete function does not erase, wipe or overwrite the information beyond recovery.
When you delete a file, the operating system does not destroy the file contents from the disk - it only deletes some "references" on the file from some system tables. The file contents remains on disk until another file happens to overwrite it. Any software recovery tool can restore the data if it hasn't been overwritten or thoroughly erased. Hardware recovery tools may even restore overwritten files by analyzing latent magnetic traces.
As a result, your confidential information may be lying unprotected on your disk (not wiped, overwritten or erased) and it is almost impossible to prevent it from falling into the wrong hands.
Sensitive files on your PC
You have just decided to move some sensitive files (business plans, password files, financial reports, etc.) from your hard disk to your floppy disk to make sure you are the only one that can access them. Moving the files to the floppy disk means copying them and then deleting them from the hard disk. But normal deletion is not secure - it does not really erase, overwrite and wipe the information beyond recovery. The result is that the contents of your sensitive files will remain exactly where you didn't want them: on the hard disk!
Looking for email privacy?
You have just accessed your mail account from your office. You've got some private messages that you decide to take home on a floppy disk. After copying the messages on the floppy disk, you delete the messages from the computer hard disk, as other people have access to your office computer and you don't want them to see your mail.
Bad news! The mail programs don't erase information to make sure the messages you delete are really gone. They simply ask Windows to perform the deletion. And Windows leaves the contents of deleted files on disk! This data must be securely wiped, overwritten and erased. Someone will eventually run a recovery tool on your office computer and find your deleted mail messages.
Dangerous Web surfing
You have just visited some compromising Web sites. You are aware of the fact that your Web browser has stored text and images from those sites in a special folder for quick viewing later (Internet Explorer's Temporary Internet Files or Google Chrome's cache). To hide your tracks, you use the Web browser's option to delete any temporary Internet files (or the cache) stored on your computer.
Do you think you got rid of those compromising files? Think again! They are still on disk! Disk tools like Norton Utilities can easily recover those deleted files! You'd better start thinking: How am I going to explain to my boss (or worse: my wife) why I visited those sites? It is of the utmost importance to thoroughly wipe, overwrite and erase data to ensure secure deletion.