WORM (Write Once Read Many) refers to storage media or configurations that can be written once and then read any number of times. Subsequent modification or deletion is technically prevented. In an ISMS, WORM storage is used for tamper-proof archiving — for example, audit logs, emails subject to retention requirements, or contract documents. Immutability protects record integrity and satisfies regulatory requirements. Cloud providers typically offer WORM functionality as immutable storage or object lock.