Wiping your computer
HOW TO SAFELY GET RID OF OLD COMPUTING DEVICES.
GETTING RID OF an old PC or mobile device can be remarkably fraught. Whether you’re selling, gifting, or just throwing the device out, you will need to take steps to properly and securely clean the device before you do so. You don’t want to become one of those cautionary tales about a person who had all their data and personal files published online because you didn’t bother to properly destroy your data before getting rid of the device!
Some people take this process to extremis, physically destroying hard drives with sledgehammers and drills to make sure that nobody can retrieve data. This month we’re going to look at some less radical approaches that don’t require physical destruction of your equipment.
ON FILE SYSTEMS (OR WHY THIS IS IMPORTANT)
As a starting point, you should recognise that simply deleting files is not enough. Deleted files can very often be recovered – which is handy when you accidentally delete an important file, but potentially devastating if you have, let’s say, some “self portraits” on a device that you gave away.
What many people don’t realise is that deleting a file does not actually delete the file data; it just deletes its entry in the file system.
To step back a bit, all a computer’s data storage hardware does is give the computer a place to store 1s and 0s. Your computer’s hard drive doesn’t tell the computer how to organise or manage that storage space. That’s where the file system comes in.
The device’s file system organises the storage space, serving as a kind of directory system for the raw storage space. It says, for example, “the file program.exe starts at byte number 104595636 and ends at byte 124753625.”
When you delete the file program.exe, the computing device doesn’t go and turn all those bytes to zero. It just deletes the entry in the directory, kind of like removing a name from the White Pages. Until those bits are actually overwritten, program.exe will remain on the drive. Hidden, but still there for someone who knows how to look.
That’s why you have to do more than just delete files – you have to nuke them from orbit.
Mobile platforms, being newer than PCs, have some advantages over Windows when it comes to file protection. For a start, on nearly all newer phones and tablets, encryption is enabled by default. An encrypted file system means that even if a hacker could access residual data on a device, it would be meaningless gobbledygook.
But there’s a ‘but’ here. Older Android devices are not encrypted by default. If you have a version of Android earlier than 6.0, there’s a chance that the phone or tablet is not encrypted. Even if you have a newer version, it’s worth checking.
In Android, go to Settings->Security. Tap on Encrypt device and enable encryption on the Android device you want to get rid of, if it’s not already enabled. You can also encrypt SD-cards.
If you’ve gifting or selling the device, there may be one more thing to do before you’re ready to wipe the device. In Android 5.0, Google introduced Factory Reset Protection (FRP), to stop thieves from stealing then wiping devices for resale. You’ll want to disable this – otherwise the new owner will get a screen asking for the previous owner’s (ie your) Google Account details.
FRP links your device to your Google account, so that after a factory reset it will ask you to log in with your Google account to enable the device. To disable FRP, you have to unlink the device from your Google account. In most devices, this will happen as part of the Settings-based factory reset process, but to be sure you should go to Settings->Accounts (or Settings->Google on some devices) first and delete your Google account from the device. This will disable FRP.
Once you’ve encrypted the device and disabled FRP, you’re ready to run a wipe. Go to Settings->Backup & Reset and select the
WHAT MANY PEOPLE DON’T REALISE IS THAT DELETING A FILE DOES NOT ACTUALLY DELETE THE FILE DATA; IT JUST DELETES ITS ENTRY IN THE FILE SYSTEM.
option to perform a Factory reset. You’ll get a warning, and if you proceed your device should be clean.
Remember to remove your SD Card and SIM, and the Android is good as new.
Because iOS devices are encrypted by default, and have no equivalent to Google’s Factory Reset Protection, the process for wiping an iOS device is simple. Make sure everything is backed up, then just go to Settings->General>Reset and tap on Erase all Content and Settings. You’ll get a warning page, then the device will be completely wiped. Remove the SIM, and it’s ready to give away or throw away. Properly cleaning a Windows PC can be tricky. Windows is not encrypted by default, and its file system actually makes it relatively easy to recover deleted files. That’s why “shredder” applications are popular – they do more than just delete the entry in the file system – they overwrite (often multiple times) the physical storage space ensuring that no recovery of files is possible.
Windows 10’s Reset Feature (found in Settings->Update & Security->Recovery) does
not shred files. It will delete files if you choose the Remove Everything option, but those files could be recovered with an undelete utility.
If you’re throwing away or selling the PC, and you don’t care about having a working install of Windows on it, your best option is a tool like Dban ( dban.org), a bootable utility that you can put on a flash drive or DVD disc. Other options include PC Disk Eraser ( www.
pcdiskeraser.com) and MHDD ( hddguru. com/software/2005.10.02-MHDD/).
To use these, tools, download the .ISO file from the app website. If you have a DVD burner, you can burn it to a disk just by right clicking on it. If you want to put it on a USB stick, that’s a little more complicated: you’ll have to use a tool like Rufus ( rufus.ie) to create a bootable USB stick with the ISO file.
Then insert the disc or USB stick and reboot your computer. Hopefully, the app should run and you’ll be able to use it to properly wipe the hard drive. If it doesn’t run, then you may have to go into your computer’s BIOS to change the computer’s boot order (you’ll have to consult the motherboard or device maker’s guide on how to boot into the BIOS).
If the computer is a hand me down, and you want to keep a working copy of Windows on it (and not have to completely reinstall Windows from scratch on a wiped hard drive), then you have another option: a Windows file shredder app.
We like the free and open source Eraser ( sourceforge.net/projects/eraser/), which you can use to delete and shred any personal files on the computer. You have to choose which files you want to shred manually, but it both deletes the file and comprehensively overwrites the hard drive to prevent recovery. It can also be used to shred any files in your recycle bin.
Use Eraser to delete every personal file on the hard drive, including everything in your user folder.
After you’ve done that, you can then go and run the Windows Reset tool (see above), which will restore Windows to its factory state. It should then be safe to pass on.
Encrypt the file system first.
Run a factory reset to wipe the device.
Windows Reset will delete your files, but it won’t shred them.
Dban is a bootable tool for erasing hard drives.
Eraser is a simple and effective Windows tool for shredding files.
Reset in iOS.