Degaussing is the removal or reduction of the magnetic field of a storage disk or drive. It's done using a device called a degausser, which is specifically designed for the medium being erased. When applied to magnetic storage media such as hard disks, magnetic tape or floppy disks, the process of degaussing can quickly and effectively purge an entire storage medium.
A key advantage to degaussing is that it makes data completely unrecoverable, making this method of destruction particularly appealing for dealing with highly sensitive data.
On the negative side, Rothke says, strong degausser products can be expensive and heavy, and they can have especially strong electromagnetic fields that can produce collateral damage to vulnerable equipment nearby.
In addition, degaussing can create irreversible damage to hard drives. It destroys the special servo control data on the drive, which is meant to be permanently embedded. Once the servo is damaged, the drive is unusable.
"Degaussing makes data unrecoverable, but it can damage certain media types so that they are no longer usable," Harkins says. "So if you're reusing [those media] this may not be the right method."
Once disks are rendered inoperable by degaussing, manufacturers may not be able to fix drives or honor replacement warranties and service contracts, Tero says.
There's also the issue of securing media during the process of degaussing. "If there are strict requirements that prevent exit of failed and decommissioned media from the data center, then the organization must assign physical space in the data center to secure the media and equipment for the disk eradication" process, Tero says.
The effectiveness of degaussing can depend on the density of drives, Harkins says. "We encountered that issue three or four years ago with hard drives in laptops," he says.
"Because of [technology] changes in hard drives and the size of them, we found that some of the degaussing capabilities [were] diminishing over time."
How effective the method is also depends on the people doing the degaussing. "If people make mistakes, then your control gets diminished," Harkins says. "Let's say the person responsible for degaussing drives was supposed to do it for 15 minutes, but they have to go to lunch so put it in for five minutes instead. You could have breakdowns like that." But he concedes that all three methods are susceptible to human error.