 Data sanitization

Data sanitization is a process intended to make recovery of specified data from a storage medium infeasible at a stated level of effort. The target data, medium and recovery capability are part of the claim. Ordinary file deletion may remove a file system entry while leaving content recoverable; disappearance from a directory is not evidence of sanitization.^[ref]

The NIST framework distinguishes clear, purge and destroy: they address different recovery capabilities and whether the medium remains usable. The appropriate method depends on the medium and the information-protection objective. A device-independent slogan such as “deleting a file removes all its data” ignores those conditions.^[ref]

A primary study by Simson Garfinkel and Abhi Shelat examined158 second-hand hard disk drives and found residual information on some readable devices. The study distinguished unreadable drives and warned that its sample was small relative to the larger used-drive market.^[ref] It supplies measured evidence of a disposal problem, not a timeless population-wide failure rate.

For an original scope example, suppose a document has one copy on a retired drive and one in an independent backup. Successfully sanitizing the retired drive does not sanitize the backup. The claim concerns the specified copy, not every occurrence of the information.

Similarly, verifying that an operation completed and deciding that its result adequately protects the target data are distinct judgments. The current NIST guide calls these verification and validation.^[ref]