A degausser is a device that renders magnetic storage media unreadable by exposing them to a powerful magnetic field. The process, called degaussing, irreversibly destroys data structures on hard drives, magnetic tapes, and similar media.
Degaussing is a recognized method for secure data destruction when media are disposed of or leave the organization. SSDs, flash storage, and optical media are unaffected and require different sanitization methods. For highly classified data, degaussing is often combined with physical destruction.