Write once read many (WORM) describes a
data storage device
Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are cons ...
in which information, once written, cannot be modified. This
write protection affords the assurance that the
data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...
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 "unintended consequences, 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 M ...
or
malware
Malware (a portmanteau for ''malicious software'') is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, de ...
.
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 typ ...
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 int ...
,
DVD-R
DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('b ...
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
Five- and eight-hole punched paper tape
Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop
Punched tape or perforated paper tape is a form of data storage ...
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 s ...
(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 daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
from another storage device such as a
hard disk
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with mag ...
. The non-technical end-user, however, cannot write the ROM even once but considers it part of the unchangeable
computing platform
A computing platform or digital platform is an environment in which a piece of software is executed. It may be the hardware or the operating system (OS), even a web browser and associated application programming interfaces, or other underlying ...
.
WORM was utilized for
Broker-dealer
In financial services, a broker-dealer is a natural person, company or other organization that engages in the business of trading securities for its own account or on behalf of its customers. Broker-dealers are at the heart of the securities and ...
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.
Current WORM drives
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 int ...
,
DVD-R
DVD recordable and DVD rewritable are optical disc recording technologies. Both terms describe DVD optical discs that can be written to by a DVD recorder, whereas only 'rewritable' discs are able to erase and rewrite data. Data is written ('b ...
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, which uses the
Universal Disk Format (UDF) file system, these discs often use a
file system
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one lar ...
that permits additional
files
File or filing may refer to:
Mechanical tools and processes
* File (tool), a tool used to ''remove'' fine amounts of material from a workpiece
**Filing (metalworking), a material removal process in manufacturing
** Nail file, a tool used to gent ...
, 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 San ...
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
Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electroma ...
tags.
"Holst Centre reports major step towards organic RFID"
/ref>
Notes
{{Reflist, group="Note"
References
Optical computer storage