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Secure deletion of data – Comparison of Degausser Types

Reasons to securely and permanently delete data

As we have discussed in this blog previously, there are several reasons why corporate and private computer users alike have to delete their stored data. For corporate, storing data beyond the data lifespan can cause unnecessary costs and in several cases, it is even mandatory to securely erase the data after a fixed time period. Additionally, when a firm wants to change their storage system or hard disks, the data on the old hardware must also be deleted properly. This said, the reason for securely deleting data is obvious – but in what situations should one decide to degauss?

The main difference between using a software erasure tool like Blancco Erasure Software and a hardware degausser is that the media which was overwritten by software with a variable bit pattern can be reused again after the procedure. This is not the case with a degausser. After degaussing, the media is permanently destroyed and can only be used for metal recycling. Another important difference between the two erasure methods is that erasure software tools cannot be used on broken hard drives or any magnetic tape media. When the hard drive  cannot be accessed by the software because it is broken, then the only solution to securely remove business critical data from the device is to use a hardware degausser. Additionally, there are no software erasure tools currently on the market which can access used magnetic tapes. Here – again – degaussing is the way to go.  Remember, the risk of data being recovered by criminals and then used against the original owner is a risk no company can take. Individuals also face the risk of being blackmailed, stolen identity and theft, when they just dispose or sell their old hardware with data still intact.

What does degaussing mean?

Hard disks and magnetic tapes use magnetic fields to store data on either the so called platters or on the tape. When degaussed, the magnetic fields are destroyed. Additionally, the degausser destroys all magnetic fields on the disks items, sectors and all data.

Different technologies used in degaussing

There are four main types of degausser technologies developed: The Conveyor Belt Degausser, the AC-Degausser, the Permanent-Magnet-Degausser and the Impulse-Degausser.

The Conveyor Belt Degausser

The Conveyor Belt Degausser works with an electromagnet underneath a conveyor belt. The devices are hovered over the electromagnet and the magnetic field will be destroyed and with it all of the data.

Problem: This procedure has to be done several times since it is not certain that all of the sectors of the device were targeted and the data was securely deleted. Additionally the hard disks have to be switched from top to bottom in this process, either manually or by the machine.

The AC-Degausser

The AC-Degausser looks like a scanner device with a glass surface, where the hardware – either a hard disk or a tape – will be placed on. As with the Conveyor Belt Degausser one strong electromagnet is directly placed underneath the middle of the glass plate. When degaussing, the user has to lay the disk or the tape directly over the glass and turn it several times.

Problem: There are several pitfalls to this technology. It is a totally manual operation which has to be done several times since one cannot be certain that the whole device is totally freed from data in one pass. Additionally, it is advised that the user should wear protective hand gloves since he gets in near contact with the magnetic field while he is turning the disks or tapes over the glass. For some time now doctors and researchers have warned about the risk of getting cancer if one is excessively exposed to magnetic fields.

The Permanent-Magnet-Degausser

This Hardware works with two rare natural magnets with high field strengths. The medium which is to be erased will be moved between the two magnets thus deleting all data.  The magnets are “always on”.

Problem: Since the magnets are always active, the hardware has to be secure from allowing  magnetic fields to ‘leak’ out of the hardware and to the user. To protect against this most of these devices are quite big and therefore are only useable in one specific place.

The Impulse-Degausser

The Impulse-Degausser uses an electro-magnetic coil. Once started, it sends a high frequency electro-magnetic impulse – via built-in and fully loaded capacitors – through the coil, which destroys all data on the disk or tape. The medium to be erased is put inside the coil to cover all of the plates with the magnetic field. With this technology hardware degaussers can be built relatively small, easy to transport and are less energy consuming than the other technologies used.

Problems: None. Since the magnetic fields are only active for a couple of seconds there is almost no risk or harm for the user. Kroll Ontrack´s Eraser Degausser is an impulse-type degausser.

The “mixed” Impulse/Permanent Magnet Degausser

This Technology uses both permanent built-in magnets to delete data and additionally sends an impulse through a coil to “finalise” the process.

Problem: Even though the idea is great it gives no additional benefit to the customer beyond a single degaussing solution. Also the cost is normally higher than a device with just one technology built in.

Summary: From a technical standpoint only two of the methods described in this article are safe enough to cover most legal and regulatory requirements: The Permanent-Magnet-Degausser and the Impulse-Degausser. But even with this knowledge it is wise to check when purchasing such a device what standards the degausser observes and what federal organisations recommend the use of it (e.g. DOD (Department of Defense), NATO, NSA, FBI, BSI etc.     

More Information about degausser technologies can be found here:



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