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A patch is
data Data ( , ) are a collection of discrete or continuous values that convey information, describing the quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted for ...
that is intended to be used to modify an existing software resource such as a program or a file, often to fix bugs and security vulnerabilities. A patch may be created to improve functionality,
usability Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a softw ...
, or
performance A performance is an act or process of staging or presenting a play, concert, or other form of entertainment. It is also defined as the action or process of carrying out or accomplishing an action, task, or function. Performance has evolved glo ...
. A patch is typically provided by a vendor for updating the software that they provide. A patch may be created manually, but commonly it is created via a tool that compares two versions of the resource and generates data that can be used to transform one to the other. Typically, a patch needs to be applied to the specific version of the resource it is intended to modify, although there are exceptions. Some patching tools can detect the version of the existing resource and apply the appropriate patch, even if it supports multiple versions. As more patches are released, their cumulative size can grow significantly, sometimes exceeding the size of the resource itself. To manage this, the number of supported versions may be limited, or a complete copy of the resource might be provided instead. Patching allows for modifying a compiled (
machine language In computer programming, machine code is computer code consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). For conventional binary computers, machine code is the binaryOn nonb ...
) program when the
source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...
is unavailable. This demands a thorough understanding of the inner workings of the compiled code, which is challenging without access to the source code. Patching also allows for making changes to a program without rebuilding it from source. For small changes, it can be more economical to distribute a patch than to distribute the complete resource. Although often intended to fix problems, a poorly designed patch can introduce new problems (see software regressions). In some cases updates may knowingly break the functionality or disable a device, for instance, by removing components for which the update provider is no longer licensed. Patch management is a part of lifecycle management, and is the process of using a strategy and plan of what patches should be applied to which systems at a specified time. Typically, a patch is applied via programmed control to
computer storage Computer data storage or digital data storage is a technology consisting of computer components and Data storage, recording media that are used to retain digital data. It is a core function and fundamental component of computers. The cent ...
so that it is permanent. In some cases a patch is applied by a
programmer A programmer, computer programmer or coder is an author of computer source code someone with skill in computer programming. The professional titles Software development, ''software developer'' and Software engineering, ''software engineer' ...
via a tool such as a
debugger A debugger is a computer program used to test and debug other programs (the "target" programs). Common features of debuggers include the ability to run or halt the target program using breakpoints, step through code line by line, and display ...
to
computer memory Computer memory stores information, such as data and programs, for immediate use in the computer. The term ''memory'' is often synonymous with the terms ''RAM,'' ''main memory,'' or ''primary storage.'' Archaic synonyms for main memory include ...
in which case the change is lost when the resource is reloaded from storage.


Types


Binary patches

Patches for
proprietary software Proprietary software is computer software, software that grants its creator, publisher, or other rightsholder or rightsholder partner a legal monopoly by modern copyright and intellectual property law to exclude the recipient from freely sharing t ...
are typically distributed as
executable file In computer science, executable code, an executable file, or an executable program, sometimes simply referred to as an executable or binary, causes a computer "to perform indicated tasks according to encoded instructions", as opposed to a da ...
s instead of
source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...
. When executed these files load a program into memory which manages the installation of the patch code into the target program(s) on disk. Patches for other software are typically distributed as data files containing the patch code. These are read by a patch utility program which performs the installation. This utility modifies the target program's executable file—the program's
machine code In computer programming, machine code is computer code consisting of machine language instructions, which are used to control a computer's central processing unit (CPU). For conventional binary computers, machine code is the binaryOn nonb ...
—typically by overwriting its bytes with bytes representing the new patch code. If the new code will fit in the space (number of bytes) occupied by the old code, it may be put in place by overwriting directly over the old code. This is called an inline patch. If the new code is bigger than the old code, the patch utility will append load record(s) containing the new code to the object file of the target program being patched. When the patched program is run, execution is directed to the new code with branch instructions (jumps or calls) patched over the place in the old code where the new code is needed. On early 8-bit microcomputers, for example the Radio Shack
TRS-80 The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer developed by American company Tandy Corporation and sold through their Radio Shack stores. Launched in 1977, it is ...
, the operating system includes a PATCH/CMD utility which accepts patch data from a text file and applies the fixes to the target program's executable binary file(s). The patch code must have place(s) in memory to be executed at runtime. Inline patches are no difficulty, but when additional memory space is needed the programmer must improvise. Naturally if the patch programmer is the one who first created the code to be patched, this is easier. Savvy programmers plan in advance for this need by reserving memory for later expansion, left unused when producing their final iteration. Other programmers not involved with the original implementation, seeking to incorporate changes at a later time, must find or make space for any additional bytes needed. The most fortunate possible circumstance for this is when the routine to be patched is a distinct module. In this case the patch programmer need merely adjust the pointers or length indicators that signal to other system components the space occupied by the module; he is then free to populate this memory space with his expanded patch code. If the routine to be patched does not exist as a distinct memory module, the programmer must find ways to shrink the routine to make enough room for the expanded patch code. Typical tactics include shortening code by finding more efficient sequences of instructions (or by redesigning with more efficient algorithms), compacting message strings and other data areas, externalizing program functions to mass storage (such as disk overlays), or removal of program features deemed less important than the changes to be installed with the patch. Small in-memory machine code patches can be manually applied with the system debug utility, such as
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/Intel 8085, 85-based microcomputers by Gary Kildall of Digital Research, Dig ...
's DDT or
MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few op ...
's DEBUG debuggers. Programmers working in interpreted
BASIC Basic or BASIC may refer to: Science and technology * BASIC, a computer programming language * Basic (chemistry), having the properties of a base * Basic access authentication, in HTTP Entertainment * Basic (film), ''Basic'' (film), a 2003 film ...
often used the POKE command to alter the functionality of a system service routine or the interpreter itself.


Source code patches

Patches can also circulate in the form of source code modifications. In this case, the patches usually consist of textual differences between two source code files, called "
diff In computing, the utility diff is a data comparison tool that computes and displays the differences between the contents of files. Unlike edit distance notions used for other purposes, diff is line-oriented rather than character-oriented, but i ...
s". These types of patches commonly come out of
open-source software project Open-source software development (OSSD) is the process by which open-source software, or similar software whose Source Code Management, source code is publicly available, is developed by an open-source software project. These are software products ...
s. In these cases, developers expect users to compile the new or changed files themselves.


Large patches

Because the word "patch" carries the connotation of a small fix, large fixes may use different nomenclature. Bulky patches or patches that significantly change a program may circulate as "
service pack In computing, a service pack comprises a collection of updates, fixes, or enhancements to a software program delivered in the form of a single installable package. Companies often release a service pack when the number of individual patches to a ...
s" or as "software updates". Microsoft Windows NT and its successors (including
Windows 2000 Windows 2000 is a major release of the Windows NT operating system developed by Microsoft, targeting the server and business markets. It is the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RT ...
, Windows XP,
Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
and Windows 7) use the "service pack" terminology. Historically,
IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
used the terms "FixPaks" and "Corrective Service Diskette" to refer to these updates.


History

Historically, software suppliers distributed patches on
paper tape Five- and eight-hole wide 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 st ...
or on
punched cards A punched card (also punch card or punched-card) is a stiff paper-based medium used to store digital information via the presence or absence of holes in predefined positions. Developed over the 18th to 20th centuries, punched cards were wide ...
, expecting the recipient to cut out the indicated part of the original tape (or deck), and patch in (hence the name) the replacement segment. Later patch distributions used magnetic tape. Then, after the invention of removable disk drives, patches came from the software developer via a disk or, later,
CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains computer data storage, data computers can read, but not write or erase. Some CDs, called enhanced CDs, hold b ...
via
mail The mail or post is a system for physically transporting postcards, letter (message), letters, and parcel (package), parcels. A postal service can be private or public, though many governments place restrictions on private systems. Since the mid ...
. With widely available
Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
access,
download In computer networks, download means to ''receive'' data from a remote system, typically a server such as a web server, an FTP server, an email server, or other similar systems. This contrasts with uploading, where data is ''sent to'' a remote ...
ing patches from the developer's
web site A website (also written as a web site) is any web page whose content is identified by a common domain name and is published on at least one web server. Websites are typically dedicated to a particular topic or purpose, such as news, education, ...
or through automated software updates became often available to the end-users. Starting with Apple's
Mac OS 9 Mac OS 9 is the ninth and final major release of the classic Mac OS operating system for Macintosh computers, made by Apple Computer. Introduced on October 23, 1999, it was promoted by Apple as "The Best Internet Operating System Ever", highlight ...
and Microsoft's
Windows ME Windows Me (Millennium Edition) is an operating system developed by Microsoft as part of its Windows 9x family of Microsoft Windows operating systems. It was the successor to Windows 98, and was released to manufacturing on June 19, 2000, and t ...
, PC operating systems gained the ability to get automatic software updates via the Internet. Computer programs can often coordinate patches to update a target program. Automation simplifies the end-user's task they need only to execute an update program, whereupon that program makes sure that updating the target takes place completely and correctly. Service packs for Microsoft Windows NT and its successors and for many commercial software products adopt such automated strategies. Some programs can update themselves via the
Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
with very little or no intervention on the part of users. The maintenance of server software and of
operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...
s often takes place in this manner. In situations where system administrators control a number of computers, this sort of automation helps to maintain consistency. The application of security patches commonly occurs in this manner. With the advent of larger storage media and higher Internet bandwidth, it became common to replace entire files (or even all of a program's files) rather than modifying existing files, especially for smaller programs.


Application

The size of patches may vary from a few
byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...
s to hundreds of
megabyte The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix ''mega'' is a multiplier of (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes ...
s; thus, more significant changes imply a larger size, though this also depends on whether the patch includes entire files or only the changed portion(s) of files. In particular, patches can become quite large when the changes add or replace non-program data, such as graphics and sounds files. Such situations commonly occur in the patching of
computer game A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, controller, keyboard, or motion sensing device) to generate visual feedback from a display device, mo ...
s. Compared with the initial installation of software, patches usually do not take long to apply. In the case of
operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...
s and
computer server A server is a computer that provides information to other computers called " clients" on a computer network. This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sh ...
software, patches have the particularly important role of fixing security holes. Some critical patches involve issues with drivers. Patches may require prior application of other patches, or may require prior or concurrent updates of several independent software components. To facilitate updates, operating systems often provide automatic or semi-automatic updating facilities. Completely automatic updates have not succeeded in gaining widespread popularity in corporate computing environments, partly because of the aforementioned glitches, but also because administrators fear that software companies may gain unlimited control over their computers.
Package management system A package manager or package management system is a collection of software tools that automates the process of installing, upgrading, configuring, and removing computer programs for a computer in a consistent manner. A package manager deals wi ...
s can offer various degrees of patch automation. Usage of completely automatic updates has become far more widespread in the consumer market, due largely to the fact that
Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
added support for them, and Service Pack 2 of Windows XP (available in 2004) enabled them by default. Cautious users, particularly system administrators, tend to put off applying patches until they can verify the stability of the fixes. Microsoft (W)SUS supports this. In the cases of large patches or of significant changes, distributors often limit availability of patches to qualified developers as a
beta test The software release life cycle is the process of developing, testing, and distributing a software product (e.g., an operating system). It typically consists of several stages, such as pre-alpha, alpha, beta, and release candidate, before the fi ...
. Applying patches to
firmware In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, h ...
poses special challenges, as it often involves the provisioning of totally new firmware images, rather than applying only the differences from the previous version. The patch usually consists of a firmware image in form of binary data, together with a supplier-provided special program that replaces the previous version with the new version; a
motherboard A motherboard, also called a mainboard, a system board, a logic board, and informally a mobo (see #Nomenclature, "Nomenclature" section), is the main printed circuit board (PCB) in general-purpose computers and other expandable systems. It ho ...
BIOS In computing, BIOS (, ; Basic Input/Output System, also known as the System BIOS, ROM BIOS, BIOS ROM or PC BIOS) is a type of firmware used to provide runtime services for operating systems and programs and to perform hardware initialization d ...
update is an example of a common firmware patch. Any unexpected error or interruption during the update, such as a power outage, may render the motherboard unusable. It is possible for motherboard manufacturers to put safeguards in place to prevent serious damage; for example, the update procedure could make and keep a backup of the firmware to use in case it determines that the primary copy is corrupt (usually through the use of a
checksum A checksum is a small-sized block of data derived from another block of digital data for the purpose of detecting errors that may have been introduced during its transmission or storage. By themselves, checksums are often used to verify dat ...
, such as a CRC).


Video games

Video game A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...
s receive patches to fix compatibility problems after their initial release just like any other software, but they can also be applied to change game rules or
algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...
s. These patches may be prompted by the discovery of exploits in the
multiplayer A multiplayer video game is a video game in which more than one person can play in the same game environment at the same time, either locally on the same computing system (couch co-op), on different computing systems via a local area network, or ...
game experience that can be used to gain unfair advantages over other players. Extra features and gameplay tweaks can often be added. These kinds of patches are common in
first-person shooters A first-person shooter (FPS) is a video game genre, video game centered on gun fighting and other weapon-based combat seen from a First person (video games), first-person perspective, with the player experiencing the action directly through t ...
with
multiplayer A multiplayer video game is a video game in which more than one person can play in the same game environment at the same time, either locally on the same computing system (couch co-op), on different computing systems via a local area network, or ...
capability, and in
MMORPG A massively multiplayer online role-playing game (MMORPG) is a video game that combines aspects of a role-playing video game and a massively multiplayer online game. As in role-playing games (RPGs), the player assumes the role of a Player charac ...
s, which are typically very complex with large amounts of content, almost always rely heavily on patches following the initial release, where patches sometimes add new content and abilities available to players. Because the balance and fairness for all players of an MMORPG can be severely corrupted within a short amount of time by an exploit, servers of an MMORPG are sometimes taken down with short notice in order to apply a critical patch with a fix. Companies sometimes release games knowing that they have bugs. ''
Computer Gaming World ''Computer Gaming World'' (CGW) was an American Video game journalism, computer game magazine that was published between 1981 and 2006. One of the few magazines of the era to survive the video game crash of 1983, it was sold to Ziff Davis in 199 ...
''s Scorpia in 1994 denounced "companies—too numerous to mention—who release shoddy product knowing they can get by with patches and upgrades, and who make ''pay''-testers of their customers".


In software development

Patches sometimes become mandatory to fix problems with
libraries A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...
or with portions of
source code In computing, source code, or simply code or source, is a plain text computer program written in a programming language. A programmer writes the human readable source code to control the behavior of a computer. Since a computer, at base, only ...
for programs in frequent use or in maintenance. This commonly occurs on very large-scale software projects, but rarely in small-scale development. In open-source projects, the authors commonly receive patches or many people publish patches that fix particular problems or add certain functionality, like support for local languages outside the project's locale. In an example from the early development of the
Linux kernel The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the k ...
(noted for publishing its complete source code),
Linus Torvalds Linus Benedict Torvalds ( , ; born 28 December 1969) is a Finnish software engineer who is the creator and lead developer of the Linux kernel. He also created the distributed version control system Git. He was honored, along with Shinya Yam ...
, the original author, received hundreds of thousands of patches from many
programmer A programmer, computer programmer or coder is an author of computer source code someone with skill in computer programming. The professional titles Software development, ''software developer'' and Software engineering, ''software engineer' ...
s to apply against his original version. The
Apache HTTP Server The Apache HTTP Server ( ) is a free and open-source software, free and open-source cross-platform web server, released under the terms of Apache License, Apache License 2.0. It is developed and maintained by a community of developers under the ...
originally evolved as a number of patches that
Brian Behlendorf Brian Behlendorf (born March 30, 1973) is an American technologist, executive, computer programmer and leading figure in the open-source software movement. He was a primary developer of the Apache Web server, the most popular web server software ...
collated to improve
NCSA HTTPd NCSA HTTPd is a discontinued web server originally developed at the NCSA at the University of Illinois at Urbana–Champaign by Robert McCool and others. First released in 1993, it was among the earliest web servers developed, following Tim Bern ...
, hence a name that implies that it is a collection of patches ( "a patchy server"). The FAQ on the project's official site states that the name 'Apache' was chosen from respect for the Native American Indian tribe of
Apache The Apache ( ) are several Southern Athabaskan language-speaking peoples of the Southwestern United States, Southwest, the Southern Plains and Northern Mexico. They are linguistically related to the Navajo. They migrated from the Athabascan ho ...
. However, the 'a patchy server' explanation was initially given on the project's website.


Variants


Hotfix

A hotfix or Quick Fix Engineering update (QFE update) is a single, cumulative package that includes information (often in the form of one or more files) that is used to address a problem in a software product (i.e., a software bug). Typically, hotfixes are made to address a specific customer situation.
Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
once used this term but has stopped in favor of new terminology: General Distribution Release (GDR) and Limited Distribution Release (LDR).
Blizzard Entertainment Blizzard Entertainment, Inc. is an American video game developer and Video game publisher, publisher based in Irvine, California, and a subsidiary of Activision Blizzard. Originally founded in 1991, the company is best known for producing the h ...
, however, defines a hotfix as "a change made to the game deemed critical enough that it cannot be held off until a regular content patch".


Point release

A point release is a minor release of a software project, especially one intended to fix bugs or do small cleanups rather than add significant features. Often, there are too many bugs to be fixed in a single major or minor release, creating a need for a point release.


Program temporary fix

Program temporary fix or Product temporary fix (PTF), depending on date, is the standard
IBM International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
terminology for a single bug fix, or group of fixes, distributed in a form ready to install for customers. A PTF was sometimes referred to as a “ZAP”. Customers sometime explain the acronym in a tongue-in-cheek manner as ''permanent temporary fix'' or more practically ''probably this fixes'', because they have the option to make the PTF a permanent part of the operating system if the patch fixes the problem.


Security patches

A ''security patch'' is a change applied to an asset to correct the weakness described by a vulnerability. This corrective action will prevent successful exploitation and remove or mitigate a threat's capability to exploit a specific vulnerability in an asset. Patch management is a part of
vulnerability management Vulnerability management is the "cyclical practice of identifying, classifying, prioritizing, remediating, and mitigating" software vulnerabilities. Vulnerability management is integral to computer security and network security, and must not be ...
the cyclical practice of identifying, classifying, remediating, and mitigating vulnerabilities. Security patches are the primary method of fixing security vulnerabilities in software. Currently Microsoft releases its security patches once a month ("
patch Tuesday Patch Tuesday (also known as Update Tuesday) is an unofficial term used to refer to when Microsoft, Adobe, Oracle and others regularly release software patches for their software products. It is widely referred to in this way by the industry. Micro ...
"), and other operating systems and software projects have security teams dedicated to releasing the most reliable software patches as soon after a vulnerability announcement as possible. Security patches are closely tied to responsible disclosure. These security patches are critical to ensure that business process does not get affected. In 2017, companies were struck by a ransomware called WannaCry which encrypts files in certain versions of
Microsoft Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
and demands a ransom via BitCoin. In response to this, Microsoft released a patch which stops the ransomware from running.


Service pack

A service pack or SP or a feature pack (FP) comprises a collection of updates, fixes, or enhancements to a software program delivered in the form of a single installable package. Companies often release a service pack when the number of individual patches to a given program reaches a certain (arbitrary) limit, or the software release has shown to be stabilized with a limited number of remaining issues based on users' feedback and bug tracking such as
Bugzilla Bugzilla is a web-based general-purpose bug tracking system and testing tool originally developed and used by the Mozilla project, and licensed under the Mozilla Public License. Released as open-source software by Netscape Communications in 19 ...
. In large software applications such as office suites, operating systems, database software, or network management, it is not uncommon to have a service pack issued within the first year or two of a product's release. Installing a service pack is easier and less error-prone than installing many individual patches, even more so when updating multiple computers over a network, where service packs are common.


Unofficial patches

An unofficial patch is a patch for a program written by a third party instead of the original developer. Similar to an ordinary patch, it alleviates bugs or shortcomings. Examples are security fixes by security specialists when an official patch by the software producers itself takes too long. Other examples are unofficial patches created by the
game community A virtual community is a social network of individuals who connect through specific social media, potentially crossing geographical and political boundaries in order to pursue mutual interests or goals. Some of the most pervasive virtual commu ...
of a
video game A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...
which became unsupported.


Monkey patches

Monkey patch In computer programming, monkey patching is a technique used to dynamically update the behavior of a piece of code at run-time. It is used to extend or modify the runtime code of dynamic programming language, dynamic languages such as Smalltalk, Ja ...
ing means extending or modifying a program locally (affecting only the running instance of the program).


Hot patching

''Hot patching'', also known as ''live patching'' or ''dynamic software updating'', is the application of patches without shutting down and restarting the system or the program concerned. This addresses problems related to unavailability of service provided by the system or the program. Method can be used to update
Linux kernel The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the k ...
without stopping the system. A patch that can be applied in this way is called a ''hot patch'' or a ''live patch''. This is becoming a common practice in the mobile app space. Companies like Rollout.io use method swizzling to deliver hot patches to the iOS ecosystem. Another method for hot-patching iOS apps is JSPatch. Cloud providers often use hot patching to avoid downtime for customers when updating underlying infrastructure.


Slipstreaming

In computing, slipstreaming is the act of integrating patches (including
service pack In computing, a service pack comprises a collection of updates, fixes, or enhancements to a software program delivered in the form of a single installable package. Companies often release a service pack when the number of individual patches to a ...
s) into the installation files of their original app, so that the result allows a direct installation of the updated app. The nature of slipstreaming means that it involves an initial outlay of time and work, but can save a lot of time (and, by extension, money) in the long term. This is especially significant for administrators that are tasked with managing a large number of computers, where typical practice for installing an operating system on each computer would be to use the original media and then update each computer after the installation was complete. This would take a lot more time than starting with a more up-to-date (slipstreamed) source, and needing to download and install the few updates not included in the slipstreamed source. However, not all patches can be applied in this fashion and one disadvantage is that if it is discovered that a certain patch is responsible for later problems, said patch cannot be removed without using an original, non-slipstreamed installation source.


Software update systems

Software update systems allow for updates to be managed by users and software developers. In the 2017 Petya cyberpandemic, the financial software "MeDoc"'s update system is said to have been compromised to spread
malware Malware (a portmanteau of ''malicious software'')Tahir, R. (2018)A study on malware and malware detection techniques . ''International Journal of Education and Management Engineering'', ''8''(2), 20. is any software intentionally designed to caus ...
via its updates. On the Tor Blog, cybersecurity expert Mike Perry states that
deterministic Determinism is the metaphysical view that all events within the universe (or multiverse) can occur only in one possible way. Deterministic theories throughout the history of philosophy have developed from diverse and sometimes overlapping mo ...
, distributed builds are likely the only way to defend against malware that attacks the software development and build processes to infect millions of machines in a single, officially signed, instantaneous update. Update managers also allow for security updates to be applied quickly and widely. Update managers of
Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
such as Synaptic allow users to update all software installed on their machine. Applications like Synaptic use cryptographic checksums to verify source/local files before they are applied to ensure fidelity against malware.


Malicious updates

Some
hacker A hacker is a person skilled in information technology who achieves goals and solves problems by non-standard means. The term has become associated in popular culture with a security hackersomeone with knowledge of bug (computing), bugs or exp ...
may compromise legitimate software update channel and inject
malicious code Malware (a portmanteau of ''malicious software'')Tahir, R. (2018)A study on malware and malware detection techniques . ''International Journal of Education and Management Engineering'', ''8''(2), 20. is any software intentionally designed to caus ...
.


See also

*
Software release life cycle The software release life cycle is the process of developing, testing, and distributing a software product (e.g., an operating system). It typically consists of several stages, such as pre-alpha, alpha, beta, and release candidate, before the fi ...
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Software maintenance Software maintenance is the modification of software after delivery. Software maintenance is often considered lower skilled and less rewarding than new development. As such, it is a common target for outsourcing or offshoring. Usually, the tea ...
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Backporting Backporting is the action of taking parts from a newer version of a software system or software component and porting them to an older version of the same software. It forms part of the maintenance step in a software development process, and ...
* Dribbleware *
Patch (Unix) The computer tool patch is a Unix program that updates text files according to instructions contained in a separate file, called a ''patch file''. The patch file (also called a ''patch'' for short) is a text file that consists of a list of diffe ...
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Porting In software engineering, porting is the process of adapting software for the purpose of achieving some form of execution in a computing environment that is different from the one that a given program (meant for such execution) was originally desig ...
* Vulnerability database *
Delta encoding Delta encoding is a way of storing or transmitting data in the form of '' differences'' (deltas) between sequential data rather than complete files; more generally this is known as data differencing. Delta encoding is sometimes called delta comp ...
* SMP/E * Automatic bug fixing * Shavlik Technologies *
White hat (computer security) A white hat (or a white-hat hacker, a whitehat) is an ethical security hacker. Ethical hacking is a term meant to imply a broader category than just penetration testing. Under the owner's consent, white-hat hackers aim to identify any vulnerabilit ...
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Upgrade Upgrading is the process of replacing a product with a newer version of the same product. In computing and consumer electronics, an upgrade is generally a replacement of hardware, software or firmware with a newer or better version, in order to ...


References


External links


''The Jargon File'' entry for ''patch''


* ttps://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#the-canonical-patch-format Official Linux kernel patch format
0-Day Patch – Exposing Vendors (In)security Performance
{{Webarchive, url=https://web.archive.org/web/20140131144456/http://www.techzoom.net/publications/0-day-patch/ , date=2014-01-31 . A metric comparing patch performance of Microsoft and Apple. Software maintenance Software release