Overwrite (also known as file wiping or shredding) means to change the value of the bits on the disk that make up a file by writing random bits over the existing data. By overwriting the disk space that the file occupied, the file cannot be reconstructed easily.
One method to sanitize media is to use software or hardware products to overwrite storage space on the media with nonsensitive data. This process may include overwriting not only the logical storage location of a file(s) (e.g., File Allocation Table) to be erased or deleted but also the entire media, including all addressable locations. The security goal of the overwriting process is to replace sensitive data with nonsensitive random data. Media should be overwritten a minimum of three times using a method based on the information sensitivity contained on the media. Overwriting cannot be used for media that are damaged or not rewriteable. The media type and size may also influence whether overwriting is a suitable sanitization method.