Does formatting a hard drive make deleted files permanently irretrievable?

It makes them more difficult to retrieve, but unless you write new data over the data (sometimes called ‘zeroing’) it’s still retrievable. And people who have highly sensitive equipment and a lot of money and time to spend can still have a chance at recovering the data even then.

there is a department of defense (i think ) method that does 35 passes over empty sectors writing and re-writing zeroes as cwilbur pointed out. I don’t think it is foolproof, but it doens depend on how badly someone wants the data.

IF it is business documentation the best way to get rid of data is to put in the lake. Data can be retrieved from dead hard drives as I learned the hard and expensive way when a drive with critical data crapped out. I was backing up every Friday and lost a couple of days work that was had to be re-created from scratch under a great deal of time pressure. For $1,500 some guys in Toronto got the data for me the next day after the drive was sent to them overnight.

there is a method that is recommended for use if your company or you are giving away a computer and want to wipe the drive clean and I will look it up and post later in the weekend.

SRM

Thanks!

I suppose formatting several times won’t do it?

@Mr_M

Nope, if you format repeatedly you will only keep writing over the same area of the disk, the boot sector.

There are a couple of utility programs (quite cheap) that’ll write zeros over the free space of your disk. The OS X Disk Utility is the only onboard utility I know that offers to write something over the free disk space.

For PC you might look into PGP or Steganos.

@srmorgan

The Department of Defense standard 5520.22-M is 7 passes, 35 passes is called the “Guthenberg Method”, and at any sizeable hard drive will take days to complete. Overkill, kind off.

@taosan, thank you, I am just a dilettante, not an IT specialist.

@srmorgan

haha, no worries, 7, 35, all the same. You know more than most…

Hmmm, what kind of information do all you guys have on your hard drives? ;-)

Only way to get rid of it altogether is to physically destroy the drive. Easiest method – these things are harder to destroy than you think – is to sink about a dozen quarter-inch holes through the platter with a power drill.