Purging
The NIST SP 800-88 sanitisation level that makes data infeasible to recover even with state-of-the-art laboratory techniques, while often leaving the media reusable.
Purging is the middle of the three sanitisation methods in NIST SP 800-88, between Clear and Destroy. It applies physical or logical techniques that make recovering the target data infeasible with state-of-the-art laboratory methods, not only with ordinary software tools. Rev. 2 (2025) refers to IEEE 2883 for the acceptable logical techniques: overwrite, block erase and cryptographic erase, run through the device’s dedicated sanitize commands so they reach areas the host cannot address. The main physical technique has been degaussing of magnetic media, which the guideline now hedges, because many degaussers lack the strength for high-coercivity drives. Unlike physical destruction, a purge often leaves the media usable, although degaussing commonly disables a modern hard drive.
Purging is commonly contrasted with clearing. Clearing defends against simple, non-invasive recovery and suits media that stays inside the organisation. Purging is typically expected when media holding sensitive data will leave organisational control; for the most sensitive data, destruction may be required instead. The technique has to suit the media: degaussing has no effect on flash storage, and cryptographic erase relies on the encryption having covered all the data from the start.
Exam relevance: a scenario may describe a drive leaving the organisation and ask which level of sanitisation is appropriate. Candidates are expected to prefer purging over clearing when media leaves organisational control, and to check that the chosen purge technique works on that media type.