Wiping a hard drive means completely erasing all data stored on the drive by overwriting it with meaningless data patterns. This is done for several reasons:
To securely erase sensitive data before disposing of or recycling a hard drive. Simply deleting files or reformatting does not fully remove data which can still be recovered. Wiping overwrites all sectors to prevent recovery.1
To repurpose or donate a drive without leaving any personal data on it. Wiping ensures no traces of your data remain before giving away a drive.2
To resolve data corruption or performance issues. Wiping completely resets the drive to a factory-like state.
To uninstall malware or viruses that may have infected the boot sector or drive firmware. A full wipe removes any persistent infections.
Wiping erases all drive sectors by overwriting them multiple times with random bit patterns, making recovery of the original data nearly impossible.
Back Up Important Data First
Before wiping your external hard drive, it is crucial to back up any important data stored on it that you want to keep. This includes documents, photos, videos, music, applications, settings, and any other personal or essential files. According to Acronis, it is best to “Create three copies of your data so that it can never be wiped out by a single event”.
There are a few recommended methods to back up an external hard drive before wiping it clean:
- Copy files to another external hard drive or devices like USB flash drives
- Upload files to a cloud storage service like Google Drive or Dropbox
- Use backup software like Apple Time Machine or Windows Backup and Restore to create a backup image file
- Clone the hard drive by creating an exact sector-by-sector copy to another drive
The key is to store the backups externally so the data is not affected when you wipe the original hard drive. Be sure to verify the backups completed properly before proceeding with wiping the external hard drive.
Choose a Wiping Software
When it comes to wiping software, there are a few good options to consider:
Darik’s Boot and Nuke (DBAN) is a popular free and open source data destruction tool (Source). The pros of DBAN are that it is straightforward to use, completely wipes the hard drive, and is free. The downsides are that it is designed for internal drives, not external drives, and it can be slow on larger drives.
Active@ KillDisk is a more full-featured paid wiping tool (Source). The pros are that it works on both internal and external drives, offers multiple wipe methods, and has extra features like disk cloning. The cons are that it costs money and may have more options than a basic user needs.
Parted Magic is another free option focused on recovery and wiping (Source). The pros are ease of use, ability to create a bootable USB, and integration of other tools. The cons are it may not be as thorough for Department of Defense-level wipes.
Overall, for a simple wipe of an external drive, a free tool like DBAN is likely sufficient. For maximum flexibility and features, a paid tool like Active@ Killdisk may be preferable.
Boot from the Wiping Software
Once you have created a bootable disk or USB drive with the wiping software, you need to boot your computer from that device instead of the normal operating system. Here are the steps:
- Insert the CD/DVD or USB drive containing the wiping software into your computer.
- Restart your computer. As it is booting up, press the key to enter the boot menu. This is usually F12, F2, F10 or Delete, but consult your computer’s manual for the proper key.
- In the boot menu, select the drive containing the wiping software. This may be labeled as the CD/DVD drive, USB drive, or have the name of the software.
- The wiping software will launch into a special environment outside of your normal OS. Follow the on-screen instructions to proceed with wiping the drive.
Booting from the wiping software CD/DVD/USB is crucial, as you cannot securely erase a hard drive while it is mounted as the active system drive in Windows, macOS or Linux. The bootable environment allows you to wipe the drive completely before booting back into the OS.
If you have issues getting the wiping software to boot, you may need to adjust the BIOS/UEFI boot order to prioritize the CD/DVD or USB drive first before the hard drive with your OS. Refer to your system’s manual for instructions on changing boot order.
Select the Drive to Wipe
It is critical to select the correct drive to wipe. Accidentally wiping the wrong drive can result in catastrophic data loss. Before selecting the drive, carefully verify it is the intended external hard drive you want to reset.
Double and triple check the drive letter, name, size, and contents to confirm you have the correct one. Relying solely on the drive letter can lead to mistakes, as drive letters may change. The name, size, and contents are better identifiers.
Many wiping tools provide warnings if the selected drive contains an operating system or active partitions. Heed these warnings and verify you do not have the operating system drive selected. Some tools like DBAN offer a confirmation prompt before starting the wipe to allow a final chance to cancel.
Taking precautions to choose the correct drive will prevent disastrous data loss. When in doubt, cancel and double check. Wiping the wrong drive can make recovery very difficult or impossible.
Choose a Wiping Method
There are several secure data sanitization methods to choose from when wiping an external hard drive. Some of the most common methods include:
Quick Wipe
A quick wipe overwrites all sectors on the drive with zeros (0x00). This is fast but not extremely secure, as some data may potentially be recovered with advanced forensic tools [1].
DOD Wipe
The DOD wipe overwrites all data according to Department of Defense standards, using a preset pattern of ones and zeros. It performs the wipe up to 3 times, making data recovery very difficult [2].
Secure Erase
Secure erase utilizes drive firmware to completely erase data by overwriting the drive sectors. It is built into most modern hard drives but may not work on older drives [3].
Zero Wipe
A zero wipe fills all sectors with zeros (0x00). It provides a basic level of security and is quick, but data may still be recoverable [1].
The most secure wiping methods overwrite all sectors multiple times using DOD or other preset patterns. However, quick wipe methods may be sufficient for less sensitive data.
Start the Wiping Process
Once you have selected the wiping method, it’s time to start the process. Be aware this can take a significant amount of time depending on the size of the drive and wiping method chosen. According to one source, a 7-pass wipe on a 500GB external hard drive took over 18 hours to complete (https://discussions.apple.com/thread/8001790). For a multi-terabyte drive, expect the process to take even longer.
Make sure your computer is plugged into a power source and avoid using it for other tasks during the wipe to prevent interruptions. The wiping software will indicate when the process is complete. Do not abort the wipe prematurely unless absolutely necessary, as an incomplete wipe could leave recoverable data on the drive.
Confirm the Wipe
After the wiping process has completed, it’s crucial to verify that the drive no longer contains any previous data or remnants of files. There are a few methods to confirm the wipe was successful:
Run a disk scanning utility like WinHex to check that the drive sectors are completely filled with ones or zeros, indicating a full overwrite. This thread provides guidance on using WinHex for verification: How can I verify that my hard disk has been zeroed / wiped?
Try to access old files or folders on the drive – if you’re prompted to format the disk rather than seeing any old data, the wipe was successful. As this Quora post mentions, being unable to recover any data is the best indication of a complete wipe: How can you tell if you have wiped your hard drive completely?
Use the drive manufacturer’s disk utilities to scan for bad sectors or corrupt data. The absence of issues indicates a clean drive.
Reboot and check the drive properties to confirm it shows the expected formatted capacity with no existing partitions or data.
Performing these verification steps will ensure the external hard drive has been wiped to a like-new state with no recoverable data remnants.
Reformat the Drive
After wiping the external hard drive, it is crucial to reformat it before using it again. The wiping process erases all existing partitions and file systems from the drive. This leaves the drive in a raw, unformatted state. Reformatting creates a new file system on the wiped drive so your operating system can access it and store new files. Without reformatting, the wiped drive remains blank and unusable.
There are a few main reasons why reformatting is necessary:
- It allows you to reuse the wiped drive for storage. Without a file system, the drive has no structure to organize and save files.
- It checks for bad sectors and remaps them so the drive is free of errors.
- It divides the drive into usable partitions if you want to create multiple sections.
- It installs a file system like NTFS or exFAT so the drive is compatible with Windows, Mac, etc.
- It renews the integrity of the file system after wiping clears out all previous file system data.
Overall, reformatting prepares the wiped drive to be a clean, fresh slate for new data storage. It’s an essential step after wiping a drive before you can use it again. Completely wiping the drive provides security, while reformatting enables functionality.
Use the Reset Drive
Once the external hard drive has been completely wiped, you now have a clean slate to work with. At this point, you can reuse the external drive or dispose of it safely.
If you plan to continue using the external drive, you will need to reformat it before you can store new files on it. Refer to your operating system’s instructions for reformatting an external hard drive. Typically, you can right-click the drive, select “Format” and choose your desired file system.
With the drive reformatted, it will show up as empty storage space and you can begin saving files to it as you normally would. Be sure to backup any important data, as the reformatting process will erase everything currently on the drive.
If you no longer need the external drive and want to dispose of it, the wiping process ensures your data is safe. You can donate, sell or recycle the device without worry that personal files might be recovered. Some organizations may have drive destruction policies and physically destroy old drives before disposal. But for most consumer uses, a thorough wipe is sufficient preparation prior to disposal.
Just be absolutely certain the wipe completed successfully before treating the drive as empty. Recovering previously wiped data is difficult but not always impossible with the right tools and expertise. So err on the side of caution when assuming your old data cannot be recovered.