What Is Degaussing: Pros, Cons and Alternative?

Data destruction is a growing industrial need gaining urgency with the rise of data protection laws that obligate organizations to destroy data in accordance with stringent regulations. "Permanent data destruction" is a prerequisite or qualifying parameter for any "compliant" media sanitization technique. Degaussing is one such data destruction technique based on demagnetizing the magnetic storage media such as hard disk drives and tapes.

This article presents an in-depth insight into "what is degaussing," how it works, types of degaussers, type of media degaussing supports, etc. It also helps understand viable alternative to degaussing and why organizations should avoid degaussing or limit its use in their data destruction strategy.

What Is Degaussing?

Degaussing is a data destruction technique based on demagnetizing or neutralizing the magnetic field used for data storage in magnetic media such as hard disk drives, floppies, etc.

You can visualize the magnetic storage media as a large "magnetized surface" split into several tiny sub-micron magnetic regions using a strong local magnetic field generated using a media writing head. These magnetized domains have their own local and uniform field orientations used for storing the data. The degaussing process eliminates these local magnetic domains by neutralizing their field orientations, thereby destroying the data. 

How Is Degaussing Performed?

Degaussing is performed using a degausser machine that applies a strong magnetic field to rearrange or randomize the existing polarity (orientation) of the magnetized domains on the storage media. As a result, the data recorded on these magnetized domains is principally destroyed. However, the efficacy of a degausser depends upon its magnetic field strength vis-à-vis the media it is degaussing.

Typically, the degausser must have 2–3 times the Coercivity of the magnetic media to degauss it effectively. Coercivity is the magnetic material's resistance to alterations in its magnetic field orientation and is measured in a unit called oersted. This fact means media with higher coercivity will require more powerful degaussing equipment and, therefore, will be challenging to degauss. As per NIST SP 800-88 guidelines, the emergent magnetic media with advanced recording technologies have higher coercivities. As a result, existing degaussers may not have adequate strength to sanitize them.

Further, precise matching of the degausser's strength vis-à-vis the media coercivity is crucial for effective degaussing. Meeting these prerequisites can pose a technical difficulty. As per NIST SP 800-88 Guidelines, "degaussing renders a legacy magnetic device purged when the strength of the degausser is carefully matched to the media coercivity. Coercivity may be difficult to determine based only on information provided on the label."

Types of Degaussers

There are essentially three types of degaussers or degaussing devices based on the mechanism they use to generate the magnetic field, as follows:

1. Coil Degausser:
   The coil degausser comprises a copper wire wound on a steel core. The setup produces a strong electromagnetic field when activated using alternating current. This electromagnetic field is used to demagnetize hard drives and other types of magnetic storage media.


Image: Coil Degausser

2. Capacitive Discharge Degausser:
   This degaussing device stores electrical charge in a capacitor, discharging the energy as a strong high-frequency electromagnetic pulse to demagnetize the storage media. This process degausses the magnetic storage media, thereby destroying the data. The capacitive discharge degausser is also known as pulse degausser.
3. Permanent Magnet Degausser:
   These are natural rare-earth magnets such as neodymium magnets with extremely high field strengths. The permanent magnet is arranged in a specialized structure to degauss magnetic media such as hard drives, tapes, etc. Unlike coil or pulse degaussers, the permanent magnet degausser does not require an electrical charge.

Image: NSA Listed Degaussers

Comparison of Degaussers
The following table compares the different degaussers against specific parameters, as follows:

 
What Type of Storage Media Can be Degaussed?
The degaussing technique can sanitize the following types of magnetic storage media:

1. Hard Disk Drives: 2.5 and 3.5-inch hard disk drives
2. Tape Drives: Linear Tape-Open (LTO), Digital Linear Tape (DLT), Advanced Intelligent Tape (AIT), Quarter Inch Cartridge (QIC), etc.
3. Floppy Disks: 8-inch, ​5 1⁄4-inch, 3 1⁄2-inch floppy disks

Disadvantages and Limitations of Degaussing
There are specific shortcomings of degaussing, crucial for consideration while defining an organization's data destruction strategy, as follows:

1. Low Efficacy of Data Destruction
   As understood earlier, degaussers need to have sufficient magnetic force, carefully matched with the media coercivity, to attain successful degaussing. Also, their efficacy is based on the equipment type, i.e., electromagnetic or permanent magnet degaussers, and their appropriate usage. To quote NIST SP 800-88 Guideline – "assurance provided by degaussing depends on selecting an effective degausser, applying it appropriately and periodically spot-checking the results to ensure it is working as expected." This functional issue with degaussing could hamper the data destruction strategy that spans a diverse variety of magnetic storage media with high coercivity.
2. Limited Scope of Media Sanitization
   Degaussers can sanitize only magnetic storage media and have no effect on flash memory-based storage such as solid-state drives, USB flash drives or memory cards, etc. So, the technique is rendered useless if you need to sanitize flash storage media. The NIST SP 800-88 Guideline advises against relying on degaussing as the sole technique to sanitize flash storage devices or magnetic storage devices that also comprise non-volatile non-magnetic storage. The Guideline categorically states, "Degaussing must not be performed as a sanitization technique on flash memory-based storage devices."
3. No Scalability
   Typically, degaussers are designed to sanitize a single hard drive to a few units together, allowing no scalability. For organizations that need to sanitize more than 8-10 drives at a time, degaussing is an inefficient technique with slow turnaround and consumption of considerable manual effort and time.
4. Renders the Media Unusable and Generates E-waste
   Degaussing turns the magnetic storage media like hard disk drives, including IDE, EIDE, ATA, and SCSI drives, useless with no residual value left to allow asset reuse or resell. This fact means degaussing is probably suitable only for the "end-of-life" media. Nonetheless, it results in e-waste with associated implications for the custodian organization.
5. High Operational Costs
   Degaussers, particularly the permanent magnet variant, are innately expensive due to their physical construct and use of rare earth metals. For example, NSA-evaluated degaussers with high oersted values can cost upwards of US$40000, incurring a significant operational expense. This cost can further add up for organizations with media sanitization needs spread across multiple facilities or branches.

Data Erasure — A Viable Alternative to Degaussing

Data erasure or data wiping is a modern media sanitization technique based on overwriting the user addressable and hidden memory locations on a storage drive with binary patterns like 0s and 1s. The erasure technique destroys the data and renders it unrecoverable using multiple overwriting passes following specialized data wiping algorithms. Further, it verifies the overwriting passes to confirm the wiping efficacy against the desired outcomes.

Some of the inherent benefits and advantages of data erasure over degaussing include—

1. Wider Scope of Media Sanitization 
   The data erasure technique can sanitize a wider variety of storage media, including magnetic storage like hard disk drives and flash storage such as SSDs, USB flash drives, memory chips, phones, etc.
2. Higher Degree of Effectiveness
   Data erasure is not concerned with aspects like magnetic storage media's field strength (coercivity) or the need to precisely match the coercivity value for effective media sanitization. It is primarily a software-based technique that can wipe any storage media within its scope by implementing one or other data wiping standards (typically in the form of an algorithm). For example, professional data erasure software like BitRaser Drive Eraser can wipe hard drives, SSDs, and other storage media using 24 international standards such as NIST 800-88 Clear and Purge, US-DoD 5220.22-M, etc. By implementing an established standard, data erasure can guarantee media sanitization with systematic assurance in the form of audit trails.
3. High Scalability and Manageability
   It is possible to erase thousands of storage drives simultaneously using professional data erasure software. In contrast with degaussing, which allows limited parallel media sanitization capacity, data erasure software allows extensive scalability to meet the needs across the usage spectrum. For example, BitRaser Drive Eraser can erase up to 65000 drives and devices together in a single workflow. Further, with built-in provisions like a centralized cloud console, the tool allows data wiping across multiple Internet-enabled facilities with easy manageability.
4. Allows Media Reuse and Generate Zero E-waste
   The erased storage drive can be reused immediately with no impact on its residual value. Data erasure prepares a thoroughly sanitized storage hardware asset, ready for reallocation, exchange, return, donation, refurbishment, resell, etc. Also, there is no e-waste generation as the erased media is re-assimilated for active usage unless it is end-of-life or legacy asset that needs recycling.

Suggested Reading: Data Erasure Vs. Degaussing
Read this article to get an in-depth comparison of data erasure and degaussing and why data erasure is better than degaussing.

Ending Notes

Degaussing is an established media sanitization technique but it turns out outdated and less effective for the evolving magnetic storage media with higher coercivity. Further, it does not destroy the data stored on flash storage media. Newer techniques like data erasure provide a more effective, expansive, and scalable alternative for media sanitization in the current context. It equips organizations with a broader capability to wipe storage media with assurance.