What is Degaussing?
Degaussing is the process of applying a changing, alternating magnetic field to a magnetic storage medium such as a hard disk drive or magnetic tape in order to randomize the magnetic alignments of data. The word “degauss” comes from the name of the physicist Carl Friedrich Gauss, who worked on the ability of magnets to pull other magnets at a distance. The technique was first developed during World War II to reduce magnetic signatures of warships that could be detected by enemy mines and submarines. Degaussing became common practice for magnetic data erasure with the rise of computers using hard disk drives in the 1950s and 1960s.
Degaussing works by exposing the magnetic medium to an alternating magnetic field that progressively diminishes in intensity. This has the effect of randomizing the magnetization of the medium, eliminating any previously stored data. The process effectively “scrambles” the magnetic domains of the media into random patterns with no preference for orientation. Once degaussing is completed, it is extremely difficult to recover or reconstruct the erased data. While degaussing does not provide the same level of security as physical destruction, it is an effective method for fast and safe erasure of magnetic media (Wikipedia).
Why Degauss Drives?
Degaussing is an effective data destruction method for hard drives and other magnetic storage media. There are several reasons degaussing may be preferred over other options like physical destruction or data wiping:
Degaussing completely removes all data by demagnetizing the drive. This process is instant and irreversible, unlike software wiping which can take hours and may not fully sanitize remnant data (according to the V91 HD/DLT Datasheet). Degaussing also destroys the drive itself, eliminating the possibility of data recovery, whereas physical destruction alone may leave recoverable data intact.
Degaussing is recommended when repurposing or disposing drives that contained sensitive information like financial records, healthcare data, classified data, or personal information. It provides a fast, efficient way to permanently sanitize drives without the risks of software wiping. Organizations that handle confidential data often rely on degaussing as part of a comprehensive data security plan.
Effectiveness of Degaussing
When done properly, degaussing is an effective way to permanently erase all data stored on a hard drive or other magnetic storage media. The strong magnetic field generated by a degausser scrambles and randomizes the magnetic orientation of bits on the drive, rendering previous data unrecoverable. According to experts, even government agencies would be unable to recover data from a drive that has been degaussed correctly (https://www.quora.com/Can-you-recover-data-from-a-degaussed-hard-drive).
However, degaussing does have some limitations. If the degaussing procedure is not performed correctly with adequate field strength and duration, some data remnants may remain recoverable. Also, solid state drives (SSDs) and other non-magnetic media cannot be degaussed. Degaussing only works on traditional hard disk drives that store data magnetically. For maximum data security, degaussing should be followed by physical destruction of the drive platters to ensure no data can ever be recovered.
Degaussing Equipment
There are a few types of degaussing equipment commonly used for hard drives:
- Handheld degaussing wands – These are handheld wands that you can pass over the hard drive to degauss it. They are inexpensive and portable but may require multiple passes to fully degauss a drive.
- Tabletop/benchtop degaussers – These degaussers are designed to fit on a table or workbench. You insert the hard drive into a slot or chamber that exposes it to a strong magnetic field to degauss it. They offer more power and effectiveness than handheld wands.
- Conveyor/tunnel degaussers – With these degaussers, the hard drive passes through on a conveyor belt and is exposed to alternating magnetic fields. They allow for automated, high-volume degaussing.
To effectively degauss a hard drive using any of these methods, it’s important to fully expose the drive to the magnetic field. This may require degaussing it in multiple orientations or sides. The degaussing field should be strong enough to penetrate the drive’s casing and degauss the platters inside. Following the device manufacturer’s instructions is key to ensuring proper degaussing.
According to Slashdot, some organizations use specialized degaussing equipment that completely destroys hard drive data permanently by altering the magnetic fields on the platters, but this type of strong degaussing can damage the drive.1
Degaussing Standards
There are various industry standards that specify the strength or level of degaussing required to render hard drives and other magnetic media unusable. These help ensure that degaussing equipment is effective at completely removing data.
Some key standards include:
- NSA/CSS EPL-2022M – Specifies degaussing levels for purging classified magnetic media to prevent sensitive data disclosure. Requires minimum 12,000 Oe field strength.
- NIST SP 800-88 Rev 1 – U.S. federal standard for media sanitization. Specifies 1,000 Oe field for degaussing hard drives.
- VS1-01.90 – Certification standard for data eraser products from the German BSI. Specifies minimum 4,000 Oe field strength.
Vendors that manufacture degaussing equipment can have their products certified to meet these standards. Higher Oersted ratings indicate stronger magnetic fields and thus more secure degaussing capabilities.
Purchasing degaussers that are certified to these stringent standards helps ensure drives are rendered permanently unusable and data is rendered unrecoverable after degaussing.
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FAQ on degaussing and hard drive destruction methods
When Degaussing is Not Enough
Although degaussing can render hard drives unusable by erasing data, it has some limitations in completely eliminating sensitive information stored on a drive.
Degaussing may not be fully effective in erasing data from modern high-density drives with perpendicular recording techniques. The data tracks on these drives are closer together and more resistant to degaussing fields (1).
Also, degaussers may fail to penetrate and erase data on larger form factor modern drives with greater platters and recording surfaces (2). This leaves the possibility of residual readable data remaining.
In cases where complete and irrecoverable data destruction is critical, degaussing should be followed up with multi-pass software overwriting. This overwrites all sectors on a drive multiple times with random data to guarantee erasure (3). Software overwriting provides a fool-proof means of sanitization when degaussing alone may not suffice.
Before disposing of or reusing degaussed drives, performing multi-pass software overwriting provides an extra layer of protection in eliminating any traces of old data.
Sources:
(1) https://phiston.com/why-degaussers-are-becoming-outdated-2/
(2) https://www.bitraser.com/article/data-erasure-vs-degaussing.php
(3) https://www.bitraser.com/article/what-is-degaussing.php
Reusing Degaussed Drives
One common question about degaussing hard drives is whether the drive is still functional and can be reused after degaussing. The degaussing process erases all data by exposing the drive to a strong magnetic field, but it typically does not damage the drive hardware itself.
After degaussing, the hard drive can technically still be powered on and used again in a computer. However, the performance will be significantly degraded compared to a new drive. The extreme magnetic field scrambles the orientation of magnetic domains on the drive platters, which makes it difficult for the read/write heads to properly interact with the surface.
This results in very slow operation as the drive struggles to read and write data. The performance degradation will be most noticeable for sequential operations like copying large files. Random access performance may be less affected in some cases.
Overall, while a degaussed hard drive can still mechanically function, its performance is poor enough that it is not recommended for reuse in most situations. The degaussing process effectively renders the drive unreliable for regular use, even though it remains physically intact. The best practice is to securely erase and reformat degauss drives before reusing if possible.
Some key exceptions where a degaussed drive may still be usable include:
- As a disposable scratch drive for very temporary storage
- In read-only applications that do not require good write performance
- For testing and experimentation purposes
In summary, degaussing is specifically intended to sanitize drives for disposal, not to erase and prepare them for reuse. While degauss drives can technically still operate, their performance is too degraded for most applications.[1]
Securely Erasing Degaussed Drives
Degaussing a drive renders the data unreadable by making up for any residual magnetism. However, it does not remove the data entirely or prevent it from being recovered using forensic techniques. For absolute data destruction and to prevent any chance of recovery, degaussing should be followed up with a secure erase.
After degaussing, the drive should be securely wiped using software that overwrites the data multiple times. At least 3 passes are recommended, with the first pass using random data, the second pass using binary 1’s, and the third pass using binary 0’s. This ensures all underlying data is completely overwritten.
The erase process should involve the entire drive, not just certain sectors or partitions. Some degaussing devices offer a built-in secure erase feature, allowing the degaussing and wiping to be performed in one integrated process.
Once the secure erase is complete, the drive sectors should be remapped and a new partition table written. This helps eliminate any residual signatures left over from initial formatting.
The effectiveness of the wiping process should be verified through disk analysis tools or drive diagnostics that check for any remaining data signatures. The drive should show no readable data left, indicating a complete and successful wipe.
Following these best practices ensures previously degaussing drives are securely erased and unrecoverable before reuse or disposal.
Disposing of Degaussed Drives
Once a hard drive has been degaussed, a decision needs to be made on how to dispose of it. There are two main options:
Recycling – Degaussed hard drives can potentially be recycled or reused, depending on the degaussing method used. However, extreme care should be taken before reusing a degaussed drive, as data may still be recoverable in some cases. Organizations like Secure Data Recovery recommend destroying the drive or further sanitizing it with software before reuse.
Destruction – Physically destroying degaussed hard drives by shredding or crushing them is the most secure option for asset disposal. This ensures no data can ever be recovered from the drive. Many organizations require physical destruction of drives containing sensitive data as part of their security policies. Secure shredding services like Proton Data can provide certified on-site hard drive destruction.
Organizations should follow industry best practices such as NIST 800-88 guidelines when disposing of IT assets like degaussed hard drives. Proper documentation, chain of custody, and validation of data sanitization should be maintained throughout the process.
Degaussing in a Data Security Plan
Degaussing plays an important role in a layered data security approach. While degaussing renders data unrecoverable, it should be used in conjunction with other security measures like encryption, access controls, and physical security.
Organizations should have policies and procedures in place outlining when degaussing should be utilized, such as before disposing of old hard drives or repurposing devices. Proper degaussing procedures should be documented and staff trained accordingly. Standards like NIST 800-88 provide best practices for sanitizing media using degaussing.
After degaussing, drives should be physically destroyed or securely erased before reuse or disposal. An auditable chain of custody should track drives from inventory through degaussing and destruction. Degaussing policies aid compliance with regulations like HIPAA and GDPR.
By incorporating degaussing into a holistic data security plan with layered controls, organizations can effectively mitigate risks of data breach and non-compliance.