WORM is a data storage technology, it allows data to be written to a storage medium a single time and prevents the data from being erased or modified. Data stored on a WORM-compliant device is considered immutable; authorized users can read the data as often as needed, but they cannot change it. Immutable storage plays a pivotal role in meeting data security and compliance requirements and protecting against ransomware and other threats.

Storage media that support WORM storage are purposely non-rewritable to prevent anyone from intentionally or accidentally erasing or modifying the data after it is initially stored. Because of this feature, government agencies and enterprises have long used WORM devices for archival purposes. Organizations subject to compliance rules find the technology useful. For example, the Securities and Exchange Commission requires brokers and dealers to retain their digital records on storage media that preserves the records in a non-rewritable, non-erasable format.