The rules for destroying sensitive or classified magnetic computer media, like hard drives and tape cartridges, often confuses folks. The reality isn’t all that complicated, certainly not as complicated as the computer equipment itself.
One question that often comes up is about what is and isn’t magnetic media. Magnetic media always involves a material with a surface that holds information in the form of magnetic traces. That includes standard hard drives, tape cartridges, Zip and Jaz disks, and jump drives. It does not include optical media (CD, DVD) or solid state storage devices (SS hard drives, flash memory sticks, thumb drives, etc.). This is important to understand, since degaussers are only useful for use on magnetic media. They can’t be used to wipe information off of optical or solid state storage devices.
There are two basic types of equipment used for destroying magnetic media: degaussers and physical destroyers, like crushers or shredders. For users with government classified data, the choice is simple- the media must be wiped using an NSA listed degausser before disposal. The NSA does not permit physical shredding or crushing as a process for final disposal of classified magnetic media. Approved degaussers can be identified by consulting the NSA Degausser Evaluated Products List or by looking at the SEM Web site under degaussers.
So, what use is there for physical magnetic media destroyers? There are two common uses. For unclassified media, a physical destroyer can be used as the sole destruction method. Devices that crush or shred hard drives and tape cartridges make these items extremely difficult to extract data from. A physical destruction method can be faster and lower cost than degaussing. This process is often seen as the best choice, when one is not concerned with an adversary with extensive resources available to recover data from scraps.
Another common use for physical destroyers is as a “step two” after degaussing. Media looks no different after degaussing. It looks just like the original classified item. For peace of mind, and as an additional safeguard, many government organizations will physically destroy media after degaussing. Physical destruction after degaussing is not currently required by the NSA, but they highly recommend it, as indicated in their storage device declassification manual. Many government agencies have set their own standards for physically destroying media after degaussing. Ultimately it is a decision for each organization whether to physically destroy degaussed media, and which device to use for that purpose. There is no NSA standard for it, and no evaluated products list to choose from.