When it’s time to get rid of an old computer or hard drive, you may want to ensure that all of the data on it is completely erased and unrecoverable. Simply deleting files or even formatting the drive isn’t enough to prevent someone from being able to recover your personal information. To fully wipe a hard drive, you’ll need to use disk utility software to overwrite the data multiple times.
Why you should wipe a hard drive before disposal
There are a few key reasons why you should take steps to fully wipe a hard drive before disposing of it:
- Prevent identity theft – If someone gets ahold of your old hard drive, they may be able to recover personal and financial information using recovery software. Wiping the drive helps ensure this can’t happen.
- Remove sensitive information – If you’re getting rid of a work computer, you want to be sure proprietary company data isn’t still accessible on it.
- Avoid future problems – If you donate, sell or recycle your old computer, you want to avoid any possibility of the new owner uncovering private files you may have forgotten were on there.
- It’s quick and easy – With the right software, wiping a hard drive fully only takes a few hours at most.
Taking the time to do a full wipe of any drives you’re disposing of gives you peace of mind that your data has been securely removed.
How data is stored on a hard drive
To understand how to wipe a hard drive effectively, it helps to first understand how data storage on a hard drive works. Hard drives store data magnetically on platters inside the drive enclosure. A read-write head floats just above the platters and changes their magnetic orientation to write data. Each change in magnetic orientation represents a 1 or 0 to store data.
When you first save a file to your hard drive, it gets written to available open sectors on the disk platters. That file gets referenced in the file allocation table (FAT) which keeps track of used and unused sectors. When you delete a file, it simply removes the reference to it in the FAT so the sectors it occupies are marked as available again to be overwritten with new data.
The data itself doesn’t get erased right away, which is why it’s possible to recover deleted files using recovery software if the sectors haven’t been overwritten yet. So to fully wipe a hard drive, the new data has to overwrite every sector to replace the previously stored data entirely.
Multiple overwrites are necessary for secure wiping
Simply overwriting the hard drive once with new data isn’t always enough to prevent data recovery. Advanced forensic data recovery tools are sometimes capable of recovering data even after it has been overwritten once on some types of drives.
To counter this, secure data wiping utilities will overwrite drives multiple times. This involves writing alternating patterns of 1s and 0s, random data, and then verification passes to ensure every sector has been wiped completely. The minimum number of passes recommended by data security experts is three, but many utilities offer options up to 35 overwrite passes or more.
Steps to securely wipe a hard drive
Here are the basic steps involved to securely wipe a hard drive using disk utility software:
- Delete any partitions and reformat the hard drive – This will remove file system references and ensure maximum surface area for overwriting.
- Run a secure erase utility – Specify the hard drive to wipe and choose a multipass overwrite option (minimum of 3 passes recommended).
- Overwrite the drive – The utility will sequentially overwrite every sector on the drive with random data patterns.
- Verify – A final pass will verify each sector has been successfully overwritten, ensuring no data remnants remain.
- Degauss (optional) – For maximum data destruction, you can degauss the drive to scramble the magnetic field after wiping.
The overwrite process can take several hours depending on the drive size and number of passes selected. But once completed, you can be confident no trace of your data remains.
Tools to securely erase hard drives
There are a variety of free and paid tools available to securely overwrite hard drives. Here are some top options:
| Utility | Platform | Features |
|---|---|---|
| Darik’s Boot and Nuke (DBAN) | Windows/Mac/Linux | Free open source tool, boots from USB/CD to wipe drive |
| Active@ KillDisk | Windows/Linux | Affordable paid tool with multiple erase methods |
| Parted Magic | Linux | Contains wiping tools with DoD 5220.22-M compliance |
| Apple FileVault | MacOS | Full disk encryption tool built into Macs |
| Enhanced Secure Erase | Windows | ATA command method supported on newer drives |
Look for a tool that supports the drive interface and offers multiple overwrite passes for maximum security.
How governments and organizations wipe hard drives
Government agencies and corporations with highly sensitive data have even more stringent requirements when it comes to drive wiping and destruction. Many adhere to standards like the US Department of Defense 5220.22-M regulation for securely erasing classified data.
Some of the ways these organizations wipe and dispose of data storage devices include:
- Degaussing – Uses strong magnetic fields to scramble drive platters and erase data.
- Physical destruction – Shredding, crushing or incinerating hard drives.
- Maintenance tracking – Managing drive wiping with serialized asset tags on drives.
- Verification – Confirming successful data erasure with certification reports.
- Witness requirements – Having designated observers present during the wiping process.
These stringent standards ensure no data can ever be recovered from the devices. Consumer-grade wiping utilities implement some of these methods on a smaller scale.
Tips for effective hard drive wiping
Follow these tips to help ensure your drive wiping process is effective:
- Use wiping software, not just file deletion or formatting – This is the only way to overwrite all sectors.
- Choose a multipass overwrite option – At least 3 passes is recommended, more for highly sensitive data.
- Wipe external drives too – Don’t forget about external hard drives, SSDs and USB sticks.
- Check for hidden sectors – Some tools can wipe HPA/DCO hidden sectors missed in OS formats.
- Verify – Double check the report at the end to confirm the wipe completed successfully.
- Destroy or reformat when done – A wiped drive can’t be used again without reformatting.
Alternatives to traditional drive wiping
While overwriting sectors multiple times is still the most widely used and recommended method to prevent data recovery, some alternatives are also starting to emerge:
- Encryption – Full disk encryption tools like BitLocker and Apple FileVault encrypt data at rest on the drive.
- Block state transitions – Emerging methods manipulate how cells transition between magnetized states.
- Degaussing – As mentioned earlier, degaussing scrambles the magnetic field to wipe drives.
- Physical destruction – If the drive platters are physically destroyed, data cannot be recovered.
However, these methods aren’t yet as established or guaranteed as traditional multi-pass overwriting for permanently and securely wiping a hard drive.
Conclusion
Wiping your hard drive using a secure erase utility with multiple overwrite passes is the most effective way to permanently destroy data when disposing of a computer or drive. Taking this important security precaution helps prevent sensitive personal or corporate data from ending up in the wrong hands.
With the right disk wiping tools, it’s a straightforward process to overwrite all sectors and securely erase everything. By following best practices and verifying the wipe procedure completed, you can ensure no unwanted data recovery is possible and safely recycle or dispose of your used drives.