How to wipe a computer easily and securely

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How to wipe a computer easily and securely

Ensure that all your personal and business data is gone before you sell or throw out a computer.

Are you selling or throwing out a laptop or desktop computer? You need to make sure that your personal and business data won’t be accessible by the buyer or anyone who decides to resurrect the old system.

Simply deleting files and folders isn’t good enough – even if you empty Windows’ Recycle Bin or Mac’s Trash Can – because it’s relatively easy to recover files using freely available tools.

Wiping then physically destroying the hard drive will ensure sensitive data can’t be accessed by anyone, but for most people, the following methods will do the job of wiping clean your old PC, laptop, Mac or Linux computer.

First, back up important data

Your old computer will contain data you may need in the future. You will need to copy this onto an external hard drive directly connected to the laptop. This is that fastest way of doing things. You could back up to the cloud, but this will take time and on slow connections, may take days. Cloud backups are great but should be done as a failsafe after you have restored data to a new system.

You will need to figure out how much storage you need. If everything is stored on one drive (usually the C: drive in Windows, right-click on the drive icon to see how much data is taking up space there.

Once you have connected the external drive to the laptop you want to wipe, you can check that it is big enough to store all the data you need.

To backup you can simply connect an external drive to the laptop and drag files and folders to it. You can use the Windows Backup feature in Windows 7 or File History in Windows 8. Windows 10 has both features and adds the ability to backup and restore system images. Mac OS, of course, offers Time Machine or you can copy files manually.

Use a third-party data destruction tool 

A specialised data destruction tool is the most secure way of wiping a computer, barring destroying the physical drive itself. And among the free tools available, we recommend DBAN, which offers a number of advanced data sanitisation methods. A third-party tool like DBAN is also the only way to securely wipe a computer running Windows 7, Vista or XP, which don’t offer the same tools as Windows 8 or later (see below).

But DBAN doesn’t need to run in any particular operating system, so it can be used to wipe just about any computer with a traditional hard disk drive. It doesn’t work with solid state drives, however, so if you need to wipe an SSD, DBAN’s developer recommends Blancco Drive Eraser (which is available as trial version and costs around A$30).

DBAN is downloadable as an ISO image so you will need to burn or extract it onto a bootable disc or USB using a tool such as 7-Zip.

Once this USB flash drive is inserted in the computer you want to wipe, restart the machine and make sure you boot from this drive (check your computer or motherboard manual if you’re not sure how to do this). Then just follow the prompts. The machine will start a several-hour-long process to securely delete everything. You can now reinstall Windows 7 from any disc or bootable USB stick with Windows installation files.

Wipe a Windows 8/8.1 computer

There are easier and still generally secure ways to wipe a computer, however. In Windows 8 or 8.1, simply go to the Start screen, find the Charms bar, click on Settings and then hit Change PC settings. Finally, choose Remove Everything and Reinstall Windows.

When you choose to erase data, make sure you click on the "thoroughly" option rather than the "quickly" so that you have a safety measure. This means the disk will be erased so you can reformat it and install a new copy of Windows automatically.

Wipe a Windows 10 computer

You're able to wipe the hard drive and installing a fresh copy of the OS on Windows 10 thanks to its built-in method.

Simply go to Start>Settings>Update & Security>Recovery and click Get Started and choose the applicable selection. In order to restore Windows 10 back to a pristine state you will have to follow the set of instructions which can be found in the applicable selection you just clicked on. In this case, choose the Remove Everything option to, surprisingly, get rid of everything.

If you have more than one drive on your laptop, you will be asked if you want files removed from all drives, and as a safety option this is the best method. Lastly, you will be asked if you want to clean the drives. This will take a few hours but will make sure that there are no files recoverable from the disk.

Wipe a Mac

Wiping a Mac has broadly similar principles and is very easy to do. If your machine is running Lion or Mountain Lion, a system disk isn't required, but for earlier Macs you will need one. To initiate the recovery partition, hold down the command and R keys as the computer restarts and open Disk Utility.

Search for the Erase tab security options and click 7-pass Erase. This will write the data to the disk several times. It might take a few hours to complete the process but is a very secure way of doing so.

Wipe a Linux computer

If you've got a Linux-based machine, wiping any of the hard drives – internal or external – is a slightly fiddly process that involves using the command line.

Open up a command line terminal and enter 'sudo fdisk -l'. This will list all the storage drives currently connected to your machine. Find the drive you want to wipe, and note the drive's device path.

Next, run this command – 'sudo dd if=/dev/zero of=/dev/sdb bs=1M' – via the terminal, making sure to substitute '/dev/sdb/' with the target drive's correct device path. This method is known as 'zeroing', and wipes the drive by overwriting every byte of information with zeroes.

There is some debate as to whether or not this is more secure than overwriting the drive with random bits of information, but it's usually quicker and is perfectly sufficient for protecting your data from the average buyer.

Alternatively, as we mentioned earlier, DBAN or Blancco can wipe any disk, no matter what operating system you’re using.

This article originally appeared at IT Pro.

Copyright © ITPro, Dennis Publishing

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