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How to Safely Wipe Data From a Mac Hard Drive

Your hard drive is likely home to a whole load of your personal data. Family photos, financial documents, emails… there’s a lot of different data types that you wouldn’t want to fall into the wrong hands. When it turns to businesses, the data stored on the drive could become even more sensitive, perhaps customer accounts or the payroll. However, what happens when the time comes to delete this data?

You might not know this, but simply pressing delete on a file doesn’t actually mean it is permanently removed from the hard drive. The system will mark the space as available for other files to overwrite, but unless something is assigned to that space then the data will still exist. A deleted file could remain on your drive for a very long time. It may not be visible to you, but there are methods people can employ to get the data back – this is essentially how data recovery works.

This is problem for users when it comes to getting rid of a hard drive. If you want to be secure, you can’t just delete everything from the drive and chuck it away. Should someone so desire, they could take the drive and run recovery programs on it and access the data that you thought had vanished.

This article will take a look on how to securely wipe all the data from your hard drive on a Mac.

First of all, open up Disk Utility. This can be located in the Applications/Utilities folder. On the left hand panel there will be a list of all your hard drives and respective partitions installed on the machine. Click the hard drive that you wish to wipe and then click ‘Security Options…’.

A dialog box will pop open called ‘Secure Erase Options’. You’ll be presented with a slider, allowing you to choose how securely you want the drive erased. The option labelled ‘Fastest’ actually just reformats, which isn’t going to be secure enough as data can still be recovered using this method. Dragging the slider up to ‘Most Secure’ will increase the number of times that the drive will be overwritten, all the way up to seven.

Basically, in order to ensure that the data is securely deleted, the drive will be overwritten with blank data a certain amount of times to ensure that nothing can be recovered. Government standards ask for a drive to be written over seven times (labelled ‘Most Secure’) on Mac, but some will tell you that this is unneeded and that a single write (the second notch on the slider) is sufficient.

There’s no harm in selecting to overwrite seven times, but be wary that the more times it writes the longer the process will take. You can’t use your computer with the drive installed while the process is being carried out, so be aware of this if you have a lot of data on your drive as you could be waiting a while.

Once you’ve selected how many times to write, click ‘Erase’ and then you’ll be asked if you’re sure. Click ‘Erase’ again and the process will start. Sometime later the process will be complete and you’ll have a clean drive, ready to throw away or reuse.


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