Tapes and hard drives used for magnetic storage media, record data by using specific magnetic patterns. A read/write head will embed data on spinning platters. The data can be effectively erased through a process called degaussing, which alters the magnetic fields used on the storage device. Whitaker Brothers' Proton T-1 Drawer Degausser is an example of a powerful degaussing device:
A hard drive can be inserted directly into the device, which has a listed processing time of 20 seconds to erase the stored data. A degausser's strong magnetic field will permanently damage the magnetic data on the storage device, either wiping it, or rearranging it into random segments.
New storage drives and tapes will have higher coercivity magnetic values, and correspondingly powerful degaussers are required to render the magnetized data on these devices inaccessible.
A drive that has been degaussed cannot be reused. The process eliminates start-up files, as well as user stored data. Degaussed tapes usually can be re-used.