The Schneier method is a software based data sanitization method used in some file shredder and data destruction programs to overwrite existing information on a hard drive or other storage device.
The Schneier data sanitization method is often implemented in the following way:
Pass 1: Writes a one
Pass 2: Writes a zero
Pass 3: Writes a stream of random characters
Pass 4: Writes a stream of random characters
Pass 5: Writes a stream of random characters
Pass 6: Writes a stream of random characters
Pass 7: Writes a stream of random characters
Erasing a hard drive using the Schneier data sanitization method will prevent all software based file recovery methods from finding information on the drive and is also likely to prevent most hardware based recovery methods from extracting information.
The Schneier method was created by Bruce Schneier and appeared in his book Applied Cryptography: Protocols, Algorithms, and Source Code in C (ISBN 978-0471128458).
Most data destruction programs support multiple data sanitization methods in addition to the Schneier method.