You can select a method of overwriting from the following:
NSA
Temporary data is overwritten twice with random numbers and once with zeros.
DoD
Temporary data is overwritten with a fixed value, the fixed value's complement, and random numbers. When completed, the overwriting is then verified.
Random Numbers
Temporary data is overwritten multiple times with random numbers. The number of overwrites can be selected from 1 to 9.
The default method for overwriting is "Random Numbers", and the default number of overwrites is 3.
NSA stands for "National Security Agency", U.S.A.
DoD stands for "Department of Defense", U.S.A.