Stefan Mileschin

To actually erase files from a magnetic hard drive, you’d have to overwrite the fill with useless data. Some tools attempt to make this easier, offering to “securely delete” a file by deleting it and overwriting its sectors with junk.

Such tools will make the specific file you “securely delete” unrecoverable. However, if you have the nuclear launch codes on your computer and need to get rid of them, just “Securely deleting” the file itself isn’t good enough.

http://www.howtogeek.com/172077/why-...ent-foolproof/