"Securely erasing a hard drive requires at least three passes"
"Securely erasing a hard drive requires randomly mixing ones and zeros"
"Securely erasing a hard drive requires 35 passes if you want to really be safe"
From my research, none of these is true. The simple facts are:
- To securely erase a mechanical (i.e. "magnetic" or "platter") hard drive, write one pass of zeroes (or ones) to the entire drive.
- To securely erase an SSD, just delete all the data. Not format. Delete.
This article nicely summarizes the research.