As I said, it writes over the entire hard disk TWICE with random data, followed by one write of zeroes, so that's three writes total. Yes, DBAN. 16 times is overkill. NIST seems to believe that medical records are securely erased after a single write. Look at this: https://en.wikipedia.org/wiki/Data_erasure#Number_of_overwrites_needed Even ATA disk wipes, widely considered to be the most secure, do a single write. But if you really want 16 writes, you could run DBAN 5 or 6 times.