Sometimes legislation or the internal guidelines of an organization demand that a certain overwriting method must be used to erase data from a storage asset. In these cases the decision is easy: Select the required method. Since standards can vary, requiring anything between 1 and 35 passes, how many overwriting rounds are required to obfuscate data on a magnetic hard disk so it cannot be recovered by any means?
Overwriting an HDD once is enough to protect against any keyboard attacks. This means that data cannot be recovered using any commercial or bespoke software. Unless the HDD contained Top Secret information or extremely valuable trade secrets, exotic data recovery attempts would be prohibitively expensive and time-consuming, so practically those won't be a problem. No one has shown complete recovery of a data sector, including the data synchronization preamble, bit de-randomizer, partial response and modulation codes, and error correction code.