Write once read many (WORM) describes a data storage device in which information, once written, cannot be modified. This

write protection Write protection is any physical mechanism that prevents writing, modifying, or erasing data on a device. Most commercial software, audio and video on writeable media is write-protected when distributed. Examples * IBM -inch magnetic tape r ...

affords the assurance that the

data In the pursuit of knowledge, data (; ) is a collection of discrete Value_(semiotics), values that convey information, describing quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of sy ...

cannot be tampered with once it is written to the device, excluding the possibility of

data loss Data loss is an error condition in information systems in which information is destroyed by failures (like failed spindle motors or head crashes on hard drives) or neglect (like mishandling, careless handling or storage under unsuitable conditions) ...

from

human error Human error refers to something having been done that was " not intended by the actor; not desired by a set of rules or an external observer; or that led the task or system outside its acceptable limits".Senders, J.W. and Moray, N.P. (1991) Human ...

or malware. On ordinary (non-WORM) data storage devices, the number of times data can be modified is limited only by the lifespan of the device, as modification involves physical changes that may cause wear to the device. The "read many" aspect is unremarkable, as modern storage devices permit unlimited reading of data once written.Historical exceptions include time-limited discs such as

Flexplay Flexplay is a trademark for a discontinued DVD-compatible optical video disc format with a time-limited (usually 48-hour) playback. They are often described as "self-destructing", although the disc merely turns black or dark red and does not ph ...

, designed for short-term rental of movies; and early

non-volatile memory Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data. Non-volatile memory typi ...

technologies such as

magnetic-core memory Magnetic-core memory was the predominant form of random-access computer memory for 20 years between about 1955 and 1975. Such memory is often just called core memory, or, informally, core. Core memory uses toroids (rings) of a hard magneti ...

and

bubble memory Bubble memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as ''bubbles'' or ''domains'', each storing one bit of data. The material is arranged to form a series o ...

, from which reading data also erased it. WORM protects the important files by keeping them safe and intact. It ensures the highest level of integrity and data security by eliminating the risk of important data from being deleted or modified. This way, the WORM helps to preserve the authenticity and safety of recorded data.

History

WORM drives preceded the invention of the

CD-R CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the i ...

, DVD-R and BD-R. An example was the IBM 3363. These drives typically used a disk in a cartridge, with an

ablative In grammar, the ablative case (pronounced ; sometimes abbreviated ) is a grammatical case for nouns, pronouns, and adjectives in the grammars of various languages; it is sometimes used to express motion away from something, among other uses. ...

optical layer that could be written to only once, and were often used in places like libraries that needed to store large amounts of data. Interfaces to connect these to PCs also existed.

Punched card A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to di ...

s and paper tape are obsolete WORM media. Although any unpunched area of the medium could be punched after the first write of the medium, doing so was virtually never useful.

Read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...

(ROM) is also a WORM medium. Such memory may contain the instructions to a computer to read the

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also i ...

from another storage device such as a hard disk. The non-technical end-user, however, cannot write the ROM even once but considers it part of the unchangeable computing platform. WORM was utilized for Broker-dealer records within the

Financial Industry Regulatory Authority The Financial Industry Regulatory Authority (FINRA) is a private American corporation that acts as a self-regulatory organization (SRO) that regulates member brokerage firms and exchange markets. FINRA is the successor to the National Associat ...

and the

U.S. Securities and Exchange Commission The U.S. Securities and Exchange Commission (SEC) is an independent agency of the United States federal government, created in the aftermath of the Wall Street Crash of 1929. The primary purpose of the SEC is to enforce the law against market ...

Current WORM drives

The

, DVD-R and BD-R

optical disc In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data (bits) in the form of pits and lands on a special material, often aluminum, on one of its flat surfaces. ...

s for computers are common WORM devices. On these discs, no region of the disc can be recorded a second time. Through

packet writing Packet writing (or incremental packet writing, IPW) is an optical disc recording technology used to allow write-once and rewritable CD and DVD media to be used in a similar manner to a floppy disk from within the operating system. Details ...

, which uses the

Universal Disk Format Universal Disk Format (UDF) is an open, vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660. Due to its design ...

(UDF) file system, these discs often use a file system that permits additional files, and even revised versions of a file by the same name, to be recorded in a different region of the disc. To the user, the disc appears to allow additions and revisions until all the disk space is used. The

SD card Secure Digital, officially abbreviated as SD, is a proprietary non-volatile flash memory card format developed by the SD Association (SDA) for use in portable devices. The standard was introduced in August 1999 by joint efforts between SanDis ...

and microSD card spec allows for multiple forms of write-protection. The most common form, only available when using a full-size SD card, provides a phsyical write protection switch which allows the user to advise the host card reader to disallow write access. This does not protect the data on the card if the card reader hardware is not built to respect the write protection switch. Multiple vendors beginning in the early 2000s developed Magnetic WORM devices. These archival grade storage devices utilize a variation of RAID and magnetic storage technologies to secure data from unauthorized alteration or modification at both the hardware and software levels. As the cost of magnetic (and solid-state) storage has decreased, so has the cost for these archival storage technologies. These technologies are almost always integrated directly into a content/document management system that manages retention schedules and access controls, along with document level history. There are multiple vendors providing Magnetic Storage technologies including NetApp, EMC Centera, KOM Networks, and others. In 2013, GreenTec-USA, Inc. developed WORM hard disk drives in capacities of 3 TB and greater. Prevention of rewrite is done at the physical disk level and cannot be modified or overridden by the attached computer.

Research

In recent years there has been a renewed interest in WORM based on organic components, such as PEDOT:PSS or other polymers such as PVK or PCz. Organic WORM devices, considered organic memory, could be used as memory elements for low-power RFID tags."Holst Centre reports major step towards organic RFID"
/ref>

Notes

{{Reflist, group="Note"

References

Optical computer storage