If it's possible for an intrusion to read from the fixed disk, and deleted source used to compile the server where the password storage security is kept raw is undeleted and read, should source code ...
Why is writing zeros (or random data) over a hard drive multiple times better than just doing it once?
Lots of different programs, such as Darik's Boot and Nuke, let you write over a hard drive multiple times under the guise of it being more secure than just doing it once. Why?
As storage technologies change over time, using different encodings and remappings to deal with sector errors, the best way to permanently erase/wipe/shred data changes also. Methods for flash drives ...