Asset Security
Asset Security covers classification-driven handling: who decides the label, what handling the label triggers, how long data is kept, and whether a sanitization method genuinely removes it. Questions usually present a scenario - a media refresh, a shared analytics store, a legal hold - and ask which control or role applies.
Roles are not interchangeable
The data owner is accountable, usually business-side, and sets classification. The steward executes classification and data-quality work day to day. The custodian implements and operates the technical controls. Users follow handling rules. If an item asks who approves a reclassification, the answer is the owner, not IT.
States and lifecycle
Data is at rest, in transit, or in use, and each state needs different controls; in-use protection such as confidential computing is a distinct control, not a variant of disk encryption. The lifecycle runs create, store, use, share, archive, destroy. Retention schedules define destruction dates, and a legal hold suspends destruction until released. Effective scoping requires a data inventory and data-flow map, because copies in backups, logs, caches, and analytics stores are the ones usually forgotten.
Sanitization vocabulary
- Clearing removes data logically and resists simple recovery but not laboratory attack.
- Purging makes recovery infeasible even with laboratory techniques: cryptographic erase or validated overwrite per NIST SP 800-88.
- Destruction is physical: shred, incinerate, or degauss.
- Degaussing works only on magnetic media; it does nothing to flash. Overwriting SSDs is unreliable because of wear levelling and over-provisioning.
Worked example
You retire 200 laptops with full-disk encryption and 50 SAN SSDs holding cardholder data. For the laptops, destroying the encryption keys renders the ciphertext unreadable - cryptographic erase, a purge. For the SSDs, degaussing is useless and overwriting is unreliable, so use the vendor sanitize command or physically destroy the drives. Record serial numbers, method, date, and an independent witness, and keep certificates. The reasoning: the method must match the physics of the media and the sensitivity of the data.
Traps that cost marks
- Treating delete or quick format as sanitization.
- Letting the custodian set classification.
- Assuming encryption removes the need for retention limits or deletion.
- Forgetting derived copies in backups, logs, and test datasets.