Degaussing involves using a machine that produces a strong electromagnetic field to destroy all magnetically recorded data. This method
of data destruction may have been effective in the past as a strong electromagnetic field was not needed to destroy data.
However, modern hard drives use thicker shielding and require a much stronger electromagnetic field in order to ensure a complete erasure.
There is no way to guarantee that a particular degassing machine will do a thorough job and therefore poses a security risk.
Different types of magnetic media require different magnetic field strength and there is a risk that an incomplete degauss might occur
if the strength used is not strong enough. Degaussing machines also destroy other components of the hard drive making it difficult to verify
the erasure process as the drives cannot be reused or tested. This significantly compromises data security and is not fully reliable.
Degaussing machines are also expensive and care must be taken to prevent nearby equipment from being destroyed.