NIST SP 800-88 Rev 2 4.5.2: Validate effectiveness: analyse errors and anomalies, assess confidentiality risk, and reject the sanitization where inaccessible areas, an inappropriate method, unqualified personnel or uncalibrated tools, substandard outcomes or too narrow a scope leave residual risk unacceptable

What does 4.5.2 require?

Validation decides whether the target data was effectively sanitized, approving the sanitization or rejecting it, in which case the method is repeated with a different technique or escalated to a more secure method. The verification results are considered; any errors, anomalies or other issues are analysed and the risks to confidentiality assessed, and unacceptable risk means the sanitization is not accepted as sufficient. Effectiveness can be undermined where part of the ISM is no longer reachable through its interface despite appearing functional; where the method or technique did not suit the media or the security category (a successfully completed degauss of an SSD sanitizes nothing); where unqualified personnel or unapproved or improperly calibrated tools were used; where the outcome misses minimum requirements (shredded optical disc pieces larger than the organisation accepts); or where the scope was too narrow (simple overwrites on an overprovisioned ISM leaving much user data untouched). The validation weighs the outcomes against how sensitive the target data is, and decides whether the effort needed to reach the data afterwards is enough to protect its confidentiality, accepting any residual risk.