How to Kill a Hard Drive

A new portable system completely cleans magnetic disks.

Researchers at the Georgia Tech Research Institute (GTRI) have developed a prototype that completely destroys a hard disk in a matter of seconds, clearing off all information and rendering the drive unusable. The disk erasure system, dubbed GuardDog, uses a 125-pound magnet that delivers a field comparable to the strength of a magnetic resonance imaging (MRI) machine. When exposed to the field, the magnetic media of a hard disk is scrubbed clean.

This prototype device is designed to erase the contents on magnetic hard disks quickly and completely, using a powerful magnetic field. The hard drive is passed through the device with a hand crank, because electrical methods would be disrupted by the magnetic field. (Courtesy of Michael Knotts, Georgia Tech Research Institute.)

The system, which currently fits inside a mini-fridge, contains an enclosed magnet with a slot large enough to accommodate a standard hard drive in its two-inch-thick steel-clad casing. The type of magnets used, called "permanent magnets," can produce a consistently intense field, says Michael Knotts, a senior research scientist at GTRI and lead researcher on the project.

Using magnets to clear hard drives isn't a new idea, says Jim Turner, senior staff research engineer at L-3 Communications ComCept, a defense contractor that collaborated on the project. However, the new system differs from other commercially available disk erasers in its speed, size, and effectiveness, he says. Consumer-grade systems rarely clean a disk entirely -- and even alternative military-grade disk-killing approaches must physically destroy the disk by grinding it into a powder to ensure complete destruction. "Given sufficient time and resources [if the disk is not physically destroyed], it is theoretically possible to reconstruct the data," Turner says.

Being able to erase drives completely and quickly could make GuardDog an effective system for the military, where a hard drive may need to be destroyed at a moment's notice, explains Knotts. Although GuardDog was driven by specific military applications, though, its technology and design could also benefit banks, credit-card companies, and other organizations with sensitive personal information, Turner adds. Millions of hard drives are retired each year, many of them housing social-security and credit-card numbers. Ideally, all the data should be scoured from the drive before it's tossed out.

GuardDog works by exploiting an extremely powerful magnetic material, called neodymium iron-boron, that produces a constant field without needing to be plugged into an electrical source or cooled to cryogenic temperatures. The strong magnetic field erases the disk by randomizing all of the magnetic dipoles in the material from their orientations when data was written to the disk. Because the field attracts steel components in the disk and its enclosure, a hand crank is used to overcome magnetic forces and pass the drive through the field. When the drive comes out, a few seconds later, the data has been removed. Knotts says that the magnet also ruins a hard-drive feature called "servo tracks" that are used to control the position of head that reads and writes data. In other words, the device not only removes the data, but also destroys the hard drive.