File Wipe programs work by not only unlinking a file but specifically overwriting them with garbage data. For very high security installations, overwiting the file several times is advised. Many government institutions have specific protocols for file deletion. For instance, the U.S. DoD (Department of Defence) 5200.28 standard defines a file to be 7 times overwritten before it is unrecoverable. Some researchers believe that the U.S. DoD standard is weak. Peter Gutmann outlines his reason for believing a file needs to be overwritten at least 22 times with different patterns in his Secure Deletion of Data from Magnetic and Solid-State Memory.
Informatika és tudomány
