87-644: A browser extension is a software module for customizing a web browser . Browsers typically allow users to install a variety of extensions, including user interface modifications, cookie management, ad blocking , and the custom scripting and styling of web pages . Browser plug-ins are a different type of module and no longer supported by the major browsers. One difference is that extensions are distributed as source code , while plug-ins are executables (i.e. object code ). The most popular browser, Google Chrome , has over 100,000 extensions available but stopped supporting plug-ins in 2020. Internet Explorer
174-506: A Chromium -based browser. (Chromium is Google's open-source project that serves as the functional core of Chrome and many other browsers.) Now that Edge has the same API as Chrome, extensions can be installed directly from the Chrome Web Store. In 2015, Mozilla announced that the long-standing XUL and XPCOM extension capabilities of Firefox would be replaced with a less-permissive API very similar to Chrome's. This change
261-532: A provider and accessed over the Internet . The process of developing software involves several stages. The stages include software design , programming , testing , release , and maintenance . Software quality assurance and security are critical aspects of software development, as bugs and security vulnerabilities can lead to system failures and security breaches. Additionally, legal issues such as software licenses and intellectual property rights play
348-569: A trojan , worm or virus ) to bypass authentication mechanisms usually over an unsecured network such as the Internet to install the backdoor application. A backdoor can also be a side effect of a software bug in legitimate software that is exploited by an attacker to gain access to a victim's computer or network. The idea has often been suggested that computer manufacturers preinstall backdoors on their systems to provide technical support for customers, but this has never been reliably verified. It
435-509: A vulnerability . Software patches are often released to fix identified vulnerabilities, but those that remain unknown ( zero days ) as well as those that have not been patched are still liable for exploitation. Vulnerabilities vary in their ability to be exploited by malicious actors, and the actual risk is dependent on the nature of the vulnerability as well as the value of the surrounding system. Although some vulnerabilities can only be used for denial of service attacks that compromise
522-520: A web application —had become the primary method that companies deliver applications. Software companies aim to deliver a high-quality product on time and under budget. A challenge is that software development effort estimation is often inaccurate. Software development begins by conceiving the project, evaluating its feasibility, analyzing the business requirements, and making a software design . Most software projects speed up their development by reusing or incorporating existing software, either in
609-457: A change request. Frequently, software is released in an incomplete state when the development team runs out of time or funding. Despite testing and quality assurance , virtually all software contains bugs where the system does not work as intended. Post-release software maintenance is necessary to remediate these bugs when they are found and keep the software working as the environment changes over time. New features are often added after
696-486: A code's correct and efficient behavior, its reusability and portability , or the ease of modification. It is usually more cost-effective to build quality into the product from the beginning rather than try to add it later in the development process. Higher quality code will reduce lifetime cost to both suppliers and customers as it is more reliable and easier to maintain . Software failures in safety-critical systems can be very serious including death. By some estimates,
783-525: A common method is exploitation of a buffer overrun vulnerability, where software designed to store data in a specified region of memory does not prevent more data than the buffer can accommodate from being supplied. Malware may provide data that overflows the buffer, with malicious executable code or data after the end; when this payload is accessed it does what the attacker, not the legitimate software, determines. Malware can exploit recently discovered vulnerabilities before developers have had time to release
870-616: A complete computer, an operating system , or a computer network that is exploited by malware to bypass defences or gain privileges it requires to run. For example, TestDisk 6.4 or earlier contained a vulnerability that allowed attackers to inject code into Windows. Malware can exploit security defects ( security bugs or vulnerabilities ) in the operating system, applications (such as browsers, e.g. older versions of Microsoft Internet Explorer supported by Windows XP ), or in vulnerable versions of browser plugins such as Adobe Flash Player , Adobe Acrobat or Reader , or Java SE . For example,
957-453: A computer system without encrypting its contents, whereas crypto ransomware locks down a system and encrypts its contents. For example, programs such as CryptoLocker encrypt files securely, and only decrypt them on payment of a substantial sum of money. Lock-screens, or screen lockers is a type of "cyber police" ransomware that blocks screens on Windows or Android devices with a false accusation in harvesting illegal content, trying to scare
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#17327797524811044-586: A digital microscope – can be used to spread malware. Devices can be infected during manufacturing or supply if quality control is inadequate. Since the rise of widespread broadband Internet access, malicious software has more frequently been designed for profit. Since 2003, the majority of widespread viruses and worms have been designed to take control of users' computers for illicit purposes. Infected " zombie computers " can be used to send email spam , to host contraband data such as child pornography , or to engage in distributed denial-of-service attacks as
1131-458: A form of extortion . Malware is used broadly against government or corporate websites to gather sensitive information, or to disrupt their operation in general. Further, malware can be used against individuals to gain information such as personal identification numbers or details, bank or credit card numbers, and passwords. In addition to criminal money-making, malware can be used for sabotage, often for political motives. Stuxnet , for example,
1218-774: A large share of the market that an exploited vulnerability concentrating on either operating system could subvert a large number of systems. It is estimated that approximately 83% of malware infections between January and March 2020 were spread via systems running Windows 10 . This risk is mitigated by segmenting the networks into different subnetworks and setting up firewalls to block traffic between them. Anti-malware (sometimes also called antivirus ) programs block and remove some or all types of malware. For example, Microsoft Security Essentials (for Windows XP, Vista, and Windows 7) and Windows Defender (for Windows 8 , 10 and 11 ) provide real-time protection. The Windows Malicious Software Removal Tool removes malicious software from
1305-443: A legal regime where liability for software products is significantly curtailed compared to other products. Source code is protected by copyright law that vests the owner with the exclusive right to copy the code. The underlying ideas or algorithms are not protected by copyright law, but are often treated as a trade secret and concealed by such methods as non-disclosure agreements . Software copyright has been recognized since
1392-521: A loader or stager. A loader or stager will merely load an extension of the malware (for example a collection of malicious functions through reflective dynamic link library injection) into memory. The purpose is to keep the initial stage light and undetectable. A dropper merely downloads further malware to the system. Ransomware prevents a user from accessing their files until a ransom is paid. There are two variations of ransomware, being crypto ransomware and locker ransomware. Locker ransomware just locks down
1479-532: A model, permissions, and a common core of APIs". However, Google joined this during its overhaul of Chrome's extension API, known as Manifest V3 , which greatly reduces the capability of ad blockers and privacy -related extensions. Thus the WebExtensions group is viewed by some extension developers as nothing more than Google imposing its Manifest V3 design. Browser extensions typically have access to sensitive data, such as browsing history , and they have
1566-426: A program could reproduce itself. This constituted a plausibility result in computability theory . Fred Cohen experimented with computer viruses and confirmed Neumann's postulate and investigated other properties of malware such as detectability and self-obfuscation using rudimentary encryption. His 1987 doctoral dissertation was on the subject of computer viruses. The combination of cryptographic technology as part of
1653-585: A quick web search . Most creative professionals have switched to software-based tools such as computer-aided design , 3D modeling , digital image editing , and computer animation . Almost every complex device is controlled by software. Malware Malware (a portmanteau of 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, deprive access to information, or which unknowingly interferes with
1740-522: A regular, benign program or utility in order to persuade a victim to install it. A Trojan horse usually carries a hidden destructive function that is activated when the application is started. The term is derived from the Ancient Greek story of the Trojan horse used to invade the city of Troy by stealth. Trojan horses are generally spread by some form of social engineering , for example, where
1827-473: A separate process . This same behavior is used by today's worms as well. With the rise of the Microsoft Windows platform in the 1990s, and the flexible macros of its applications, it became possible to write infectious code in the macro language of Microsoft Word and similar programs. These macro viruses infect documents and templates rather than applications ( executables ), but rely on
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#17327797524811914-495: A significant role in the distribution of software products. The first use of the word software is credited to mathematician John Wilder Tukey in 1958. The first programmable computers, which appeared at the end of the 1940s, were programmed in machine language . Machine language is difficult to debug and not portable across different computers. Initially, hardware resources were more expensive than human resources . As programs became complex, programmer productivity became
2001-458: A specific version of the software, downloaded, and run on hardware belonging to the purchaser. The rise of the Internet and cloud computing enabled a new model, software as a service (SaaS), in which the provider hosts the software (usually built on top of rented infrastructure or platforms ) and provides the use of the software to customers, often in exchange for a subscription fee . By 2023, SaaS products—which are usually delivered via
2088-602: A suitable patch . Even when new patches addressing the vulnerability have been released, they may not necessarily be installed immediately, allowing malware to take advantage of systems lacking patches. Sometimes even applying patches or installing new versions does not automatically uninstall the old versions. There are several ways the users can stay informed and protected from security vulnerabilities in software. Software providers often announce updates that address security issues. Common vulnerabilities are assigned unique identifiers (CVE IDs) and listed in public databases like
2175-415: A system's availability, others allow the attacker to inject and run their own code (called malware ), without the user being aware of it. To thwart cyberattacks, all software in the system must be designed to withstand and recover from external attack. Despite efforts to ensure security, a significant fraction of computers are infected with malware. Programming languages are the format in which software
2262-522: A user executes code, the system allows that code all rights of that user. A credential attack occurs when a user account with administrative privileges is cracked and that account is used to provide malware with appropriate privileges. Typically, the attack succeeds because the weakest form of account security is used, which is typically a short password that can be cracked using a dictionary or brute force attack. Using strong passwords and enabling two-factor authentication can reduce this risk. With
2349-482: A user is duped into executing an email attachment disguised to be unsuspicious, (e.g., a routine form to be filled in), or by drive-by download . Although their payload can be anything, many modern forms act as a backdoor, contacting a controller (phoning home) which can then have unauthorized access to the affected computer, potentially installing additional software such as a keylogger to steal confidential information, cryptomining software or adware to generate revenue to
2436-413: A user to access all rights of that user, which is known as over-privileged code. This was also standard operating procedure for early microcomputer and home computer systems. Malware, running as over-privileged code, can use this privilege to subvert the system. Almost all currently popular operating systems, and also many scripting applications allow code too many privileges, usually in the sense that when
2523-623: A virus causes itself to be run whenever the program is run or the disk is booted. Early computer viruses were written for the Apple II and Mac , but they became more widespread with the dominance of the IBM PC and MS-DOS . The first IBM PC virus in the wild was a boot sector virus dubbed (c)Brain , created in 1986 by the Farooq Alvi brothers in Pakistan. Malware distributors would trick
2610-480: Is a technique known as LotL, or Living off the Land. This reduces the amount of forensic artifacts available to analyze. Recently these types of attacks have become more frequent with a 432% increase in 2017 and makeup 35% of the attacks in 2018. Such attacks are not easy to perform but are becoming more prevalent with the help of exploit-kits. A vulnerability is a weakness, flaw or software bug in an application ,
2697-402: Is closely tied to the development of digital computers in the mid-20th century. Early programs were written in the machine language specific to the hardware. The introduction of high-level programming languages in 1958 allowed for more human-readable instructions, making software development easier and more portable across different computer architectures . Software in a programming language
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2784-413: Is difficult for two reasons. The first is that it is difficult to determine if software is malicious. The second is that malware uses technical measures to make it more difficult to detect it. An estimated 33% of malware is not detected by antivirus software. The most commonly employed anti-detection technique involves encrypting the malware payload in order to prevent antivirus software from recognizing
2871-497: Is insufficient consensus or data to classify them as malware. Types of greyware typically includes spyware , adware , fraudulent dialers , joke programs ("jokeware") and remote access tools . For example, at one point, Sony BMG compact discs silently installed a rootkit on purchasers' computers with the intention of preventing illicit copying. Potentially unwanted programs (PUPs) are applications that would be considered unwanted despite often being intentionally downloaded by
2958-414: Is run through a compiler or interpreter to execute on the architecture's hardware. Over time, software has become complex, owing to developments in networking , operating systems , and databases . Software can generally be categorized into two main types: The rise of cloud computing has introduced the new software delivery model Software as a Service (SaaS). In SaaS, applications are hosted by
3045-429: Is software that embeds itself in some other executable software (including the operating system itself) on the target system without the user's knowledge and consent and when it is run, the virus is spread to other executable files. A worm is a stand-alone malware software that actively transmits itself over a network to infect other computers and can copy itself without infecting files. These definitions lead to
3132-448: Is software usually hidden within another seemingly innocuous program that can produce copies of itself and insert them into other programs or files, and that usually performs a harmful action (such as destroying data). They have been likened to biological viruses . An example of this is a portable execution infection, a technique, usually used to spread malware, that inserts extra data or executable code into PE files . A computer virus
3219-402: Is then used to compare scanned files by an antivirus program. Because this approach is not useful for malware that has not yet been studied, antivirus software can use dynamic analysis to monitor how the program runs on a computer and block it if it performs unexpected activity. The aim of any malware is to conceal itself from detection by users or antivirus software. Detecting potential malware
3306-455: Is twice as many malware variants as in 2016. Cybercrime , which includes malware attacks as well as other crimes committed by computer, was predicted to cost the world economy US$ 6 trillion in 2021, and is increasing at a rate of 15% per year. Since 2021, malware has been designed to target computer systems that run critical infrastructure such as the electricity distribution network . The defense strategies against malware differ according to
3393-447: Is used to generate money by click fraud , making it appear that the computer user has clicked an advertising link on a site, generating a payment from the advertiser. It was estimated in 2012 that about 60 to 70% of all active malware used some kind of click fraud, and 22% of all ad-clicks were fraudulent. Grayware is any unwanted application or file that can worsen the performance of computers and may cause security risks but which there
3480-453: Is written. Since the 1950s, thousands of different programming languages have been invented; some have been in use for decades, while others have fallen into disuse. Some definitions classify machine code —the exact instructions directly implemented by the hardware—and assembly language —a more human-readable alternative to machine code whose statements can be translated one-to-one into machine code—as programming languages. Programs written in
3567-483: The Android platform can be a major source of malware infection but one solution is to use third-party software to detect apps that have been assigned excessive privileges. Some systems allow all users to make changes to the core components or settings of the system, which is considered over-privileged access today. This was the standard operating procedure for early microcomputer and home computer systems, where there
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3654-479: The Chrome Web Store after many users complained about unwanted pop-up ads. The following year, Google acknowledged that about five percent of visits to its own websites had been altered by extensions with adware. Software Software consists of computer programs that instruct the execution of a computer . Software also includes design documents and specifications. The history of software
3741-640: The National Vulnerability Database . Tools like Secunia PSI, free for personal use, can scan a computer for outdated software with known vulnerabilities and attempt to update them. Firewalls and intrusion prevention systems can monitor the network traffic for suspicious activity that might indicate an attack. Users and programs can be assigned more privileges than they require, and malware can take advantage of this. For example, of 940 Android apps sampled, one third of them asked for more privileges than they required. Apps targeting
3828-438: The high-level programming languages used to create software share a few main characteristics: knowledge of machine code is not necessary to write them, they can be ported to other computer systems, and they are more concise and human-readable than machine code. They must be both human-readable and capable of being translated into unambiguous instructions for computer hardware. The invention of high-level programming languages
3915-560: The ability to alter some browser settings, add user interface items, or replace website content. As a result, there have been instances of malware , so users need to be cautious about what extensions they install. There have also been cases of applications installing browser extensions without the user's knowledge , making it hard for the user to uninstall the unwanted extension. Some Google Chrome extension developers have sold their extensions to third-parties who then incorporated adware . In 2014, Google removed two such extensions from
4002-399: The bottleneck. The introduction of high-level programming languages in 1958 hid the details of the hardware and expressed the underlying algorithms into the code . Early languages include Fortran , Lisp , and COBOL . There are two main types of software: Software can also be categorized by how it is deployed . Traditional applications are purchased with a perpetual license for
4089-404: The correctness of code, while user acceptance testing helps to ensure that the product meets customer expectations. There are a variety of software development methodologies , which vary from completing all steps in order to concurrent and iterative models. Software development is driven by requirements taken from prospective users, as opposed to maintenance, which is driven by events such as
4176-400: The cost of poor quality software can be as high as 20 to 40 percent of sales. Despite developers' goal of delivering a product that works entirely as intended, virtually all software contains bugs. The rise of the Internet also greatly increased the need for computer security as it enabled malicious actors to conduct cyberattacks remotely. If a bug creates a security risk, it is called
4263-419: The cost of products. Unlike copyrights, patents generally only apply in the jurisdiction where they were issued. Engineer Capers Jones writes that "computers and software are making profound changes to every aspect of human life: education, work, warfare, entertainment, medicine, law, and everything else". It has become ubiquitous in everyday life in developed countries . In many cases, software augments
4350-405: The differences in its signatures. This is known as polymorphic malware. Other common techniques used to evade detection include, from common to uncommon: (1) evasion of analysis and detection by fingerprinting the environment when executed; (2) confusing automated tools' detection methods. This allows malware to avoid detection by technologies such as signature-based antivirus software by changing
4437-489: The fact that macros in a Word document are a form of executable code. Many early infectious programs, including the Morris Worm , the first internet worm, were written as experiments or pranks. Today, malware is used by both black hat hackers and governments to steal personal, financial, or business information. Today, any device that plugs into a USB port – even lights, fans, speakers, toys, or peripherals such as
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#17327797524814524-467: The fact that the other had been killed, and would start a new copy of the recently stopped program within a few milliseconds. The only way to kill both ghosts was to kill them simultaneously (very difficult) or to deliberately crash the system. A backdoor is a broad term for a computer program that allows an attacker persistent unauthorised remote access to a victim's machine often without their knowledge. The attacker typically uses another attack (such as
4611-438: The form of commercial off-the-shelf (COTS) or open-source software . Software quality assurance is typically a combination of manual code review by other engineers and automated software testing . Due to time constraints, testing cannot cover all aspects of the software's intended functionality, so developers often focus on the most critical functionality. Formal methods are used in some safety-critical systems to prove
4698-439: The functionality of existing technologies such as household appliances and elevators . Software also spawned entirely new technologies such as the Internet , video games , mobile phones , and GPS . New methods of communication, including email , forums , blogs , microblogging , wikis , and social media , were enabled by the Internet. Massive amounts of knowledge exceeding any paper-based library are now available with
4785-408: The host. It also limits access to system resources like memory and the file system to maintain isolation. Browser sandboxing is a security measure that isolates web browser processes and tabs from the operating system to prevent malicious code from exploiting vulnerabilities. It helps protect against malware, zero-day exploits , and unintentional data leaks by trapping potentially harmful code within
4872-467: The intention to prevent irreversible system damage. Most AVs allow users to override this behaviour. This can have a considerable performance impact on the operating system, though the degree of impact is dependent on how many pages it creates in virtual memory . Sandboxing is a security model that confines applications within a controlled environment, restricting their operations to authorized "safe" actions and isolating them from other applications on
4959-401: The latter enabled, even if an attacker can crack the password, they cannot use the account without also having the token possessed by the legitimate user of that account. Homogeneity can be a vulnerability. For example, when all computers in a network run the same operating system, upon exploiting one, one worm can exploit them all: In particular, Microsoft Windows or Mac OS X have such
5046-597: The mid-1970s and is vested in the company that makes the software, not the employees or contractors who wrote it. The use of most software is governed by an agreement ( software license ) between the copyright holder and the user. Proprietary software is usually sold under a restrictive license that limits copying and reuse (often enforced with tools such as digital rights management (DRM)). Open-source licenses , in contrast, allow free use and redistribution of software with few conditions. Most open-source licenses used for software require that modifications be released under
5133-464: The new version of Proton Remote Access Trojan (RAT) trained to extract password data from various sources, such as browser auto-fill data, the Mac-OS keychain, and password vaults. Droppers are a sub-type of Trojans that solely aim to deliver malware upon the system that they infect with the desire to subvert detection through stealth and a light payload. It is important not to confuse a dropper with
5220-402: The observation that a virus requires the user to run an infected software or operating system for the virus to spread, whereas a worm spreads itself. Once malicious software is installed on a system, it is essential that it stays concealed, to avoid detection. Software packages known as rootkits allow this concealment, by modifying the host's operating system so that the malware is hidden from
5307-432: The operating system's core or kernel and functions in a manner similar to how certain malware itself would attempt to operate, though with the user's informed permission for protecting the system. Any time the operating system accesses a file, the on-access scanner checks if the file is infected or not. Typically, when an infected file is found, execution is stopped and the file is quarantined to prevent further damage with
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#17327797524815394-472: The operating system) can take this saved file and execute it as a process on the computer hardware. Some programming languages use an interpreter instead of a compiler. An interpreter converts the program into machine code at run time , which makes them 10 to 100 times slower than compiled programming languages. Software is often released with the knowledge that it is incomplete or contains bugs. Purchasers knowingly buy it in this state, which has led to
5481-558: The operator of the trojan. While Trojan horses and backdoors are not easily detectable by themselves, computers may appear to run slower, emit more heat or fan noise due to heavy processor or network usage, as may occur when cryptomining software is installed. Cryptominers may limit resource usage and/or only run during idle times in an attempt to evade detection. Unlike computer viruses and worms, Trojan horses generally do not attempt to inject themselves into other files or otherwise propagate themselves. In spring 2017, Mac users were hit by
5568-419: The payload of the virus, exploiting it for attack purposes was initialized and investigated from the mid-1990s, and includes initial ransomware and evasion ideas. Before Internet access became widespread, viruses spread on personal computers by infecting executable programs or boot sectors of floppy disks. By inserting a copy of itself into the machine code instructions in these programs or boot sectors ,
5655-618: The physical world may also be part of the requirements for a software patent to be held valid. Software patents have been historically controversial . Before the 1998 case State Street Bank & Trust Co. v. Signature Financial Group, Inc. , software patents were generally not recognized in the United States. In that case, the Supreme Court decided that business processes could be patented. Patent applications are complex and costly, and lawsuits involving patents can drive up
5742-570: The primary method of malware delivery, accounting for 96% of malware delivery around the world. The first worms, network -borne infectious programs, originated not on personal computers, but on multitasking Unix systems. The first well-known worm was the Morris worm of 1988, which infected SunOS and VAX BSD systems. Unlike a virus, this worm did not insert itself into other programs. Instead, it exploited security holes ( vulnerabilities ) in network server programs and started itself running as
5829-408: The release. Over time, the level of maintenance becomes increasingly restricted before being cut off entirely when the product is withdrawn from the market. As software ages , it becomes known as legacy software and can remain in use for decades, even if there is no one left who knows how to fix it. Over the lifetime of the product, software maintenance is estimated to comprise 75 percent or more of
5916-424: The same license, which can create complications when open-source software is reused in proprietary projects. Patents give an inventor an exclusive, time-limited license for a novel product or process. Ideas about what software could accomplish are not protected by law and concrete implementations are instead covered by copyright law . In some countries, a requirement for the claimed invention to have an effect on
6003-399: The same or very similar API due to the popularity of Google Chrome . Chrome was the first browser with an extension API based solely on HTML , CSS , and JavaScript . Beta testing for this capability began in 2009, and the following year Google opened the Chrome Web Store . As of June 2012, there were 750 million total installations of extensions and other content hosted on the store. In
6090-429: The same year, Chrome overtook Internet Explorer as the world's most popular browser, and its usage share reached 60% in 2018. Because of Chrome's success, Microsoft created a very similar extension API for its Edge browser, with the goal of making it easy for Chrome extension developers to port their work to Edge. But after three years Edge still had a disappointingly small market share, so Microsoft rebuilt it as
6177-621: The server used by the malware; (3) timing-based evasion. This is when malware runs at certain times or following certain actions taken by the user, so it executes during certain vulnerable periods, such as during the boot process, while remaining dormant the rest of the time; (4) obfuscating internal data so that automated tools do not detect the malware; (v) information hiding techniques, namely stegomalware ; and (5) fileless malware which runs within memory instead of using files and utilizes existing system tools to carry out malicious acts. The use of existing binaries to carry out malicious activities
6264-412: The signature. Tools such as crypters come with an encrypted blob of malicious code and a decryption stub. The stub decrypts the blob and loads it into memory. Because antivirus does not typically scan memory and only scans files on the drive, this allows the malware to evade detection. Advanced malware has the ability to transform itself into different variations, making it less likely to be detected due to
6351-437: The system. Additionally, several capable antivirus software programs are available for free download from the Internet (usually restricted to non-commercial use). Tests found some free programs to be competitive with commercial ones. Typically, antivirus software can combat malware in the following ways: A specific component of anti-malware software, commonly referred to as an on-access or real-time scanner, hooks deep into
6438-431: The total development cost. Completing a software project involves various forms of expertise, not just in software programmers but also testing, documentation writing, project management , graphic design , user experience , user support, marketing , and fundraising. Software quality is defined as meeting the stated requirements as well as customer expectations. Quality is an overarching term that can refer to
6525-465: The type of malware but most can be thwarted by installing antivirus software , firewalls , applying regular patches , securing networks from intrusion, having regular backups and isolating infected systems . Malware can be designed to evade antivirus software detection algorithms. The notion of a self-reproducing computer program can be traced back to initial theories about the operation of complex automata. John von Neumann showed that in theory
6612-615: The user into booting or running from an infected device or medium. For example, a virus could make an infected computer add autorunnable code to any USB stick plugged into it. Anyone who then attached the stick to another computer set to autorun from USB would in turn become infected, and also pass on the infection in the same way. Older email software would automatically open HTML email containing potentially malicious JavaScript code. Users may also execute disguised malicious email attachments. The 2018 Data Breach Investigations Report by Verizon , cited by CSO Online , states that emails are
6699-469: The user's computer security and privacy . Researchers tend to classify malware into one or more sub-types (i.e. computer viruses , worms , Trojan horses , ransomware , spyware , adware , rogue software , wipers and keyloggers ). Malware poses serious problems to individuals and businesses on the Internet. According to Symantec 's 2018 Internet Security Threat Report (ISTR), malware variants number has increased to 669,947,865 in 2017, which
6786-894: The user. PUPs include spyware, adware, and fraudulent dialers. Many security products classify unauthorised key generators as PUPs, although they frequently carry true malware in addition to their ostensible purpose. In fact, Kammerstetter et al. (2012) estimated that as much as 55% of key generators could contain malware and that about 36% malicious key generators were not detected by antivirus software. Some types of adware turn off anti-malware and virus protection; technical remedies are available. Programs designed to monitor users' web browsing, display unsolicited advertisements , or redirect affiliate marketing revenues are called spyware . Spyware programs do not spread like viruses; instead they are generally installed by exploiting security holes. They can also be hidden and packaged together with unrelated user-installed software. The Sony BMG rootkit
6873-501: The user. Rootkits can prevent a harmful process from being visible in the system's list of processes , or keep its files from being read. Some types of harmful software contain routines to evade identification and/or removal attempts, not merely to hide themselves. An early example of this behavior is recorded in the Jargon File tale of a pair of programs infesting a Xerox CP-V time sharing system: Each ghost-job would detect
6960-623: The victims into paying up a fee. Jisut and SLocker impact Android devices more than other lock-screens, with Jisut making up nearly 60 percent of all Android ransomware detections. Encryption-based ransomware, like the name suggests, is a type of ransomware that encrypts all files on an infected machine. These types of malware then display a pop-up informing the user that their files have been encrypted and that they must pay (usually in Bitcoin) to recover them. Some examples of encryption-based ransomware are CryptoLocker and WannaCry . Some malware
7047-680: Was designed to disrupt very specific industrial equipment. There have been politically motivated attacks which spread over and shut down large computer networks, including massive deletion of files and corruption of master boot records , described as "computer killing." Such attacks were made on Sony Pictures Entertainment (25 November 2014, using malware known as Shamoon or W32.Disttrack) and Saudi Aramco (August 2012). Malware can be classified in numerous ways, and certain malicious programs may fall into two or more categories simultaneously. Broadly, software can categorised into three types: (i) goodware; (ii) greyware and (iii) malware. A computer virus
7134-482: Was enacted in 2017. Firefox extensions are now largely compatible with their Chrome counterparts. Apple was the last major exception to this trend, but support for extensions conforming to the Chrome API was added to Safari for macOS in 2020. Extensions were later enabled in the iOS version for the first time. In 2021, these browser vendors formed a new W3C community group, called WebExtensions, to "specify
7221-422: Was intended to prevent illicit copying; but also reported on users' listening habits, and unintentionally created extra security vulnerabilities. Antivirus software typically uses two techniques to detect malware: (i) static analysis and (ii) dynamic/heuristic analysis. Static analysis involves studying the software code of a potentially malicious program and producing a signature of that program. This information
7308-543: Was no distinction between an administrator or root , and a regular user of the system. In some systems, non-administrator users are over-privileged by design, in the sense that they are allowed to modify internal structures of the system. In some environments, users are over-privileged because they have been inappropriately granted administrator or equivalent status. This can be because users tend to demand more privileges than they need, so often end up being assigned unnecessary privileges. Some systems allow code executed by
7395-461: Was reported in 2014 that US government agencies had been diverting computers purchased by those considered "targets" to secret workshops where software or hardware permitting remote access by the agency was installed, considered to be among the most productive operations to obtain access to networks around the world. Backdoors may be installed by Trojan horses, worms , implants , or other methods. A Trojan horse misrepresents itself to masquerade as
7482-401: Was simultaneous with the compilers needed to translate them automatically into machine code. Most programs do not contain all the resources needed to run them and rely on external libraries . Part of the compiler's function is to link these files in such a way that the program can be executed by the hardware. Once compiled, the program can be saved as an object file and the loader (part of
7569-571: Was the first major browser to support extensions, with the release of version 4 in 1997. Firefox has supported extensions since its launch in 2004. Opera and Chrome began supporting extensions in 2009, and Safari did so the following year. Microsoft Edge added extension support in 2016. In 2015, a community group formed under the W3C to create a single standard application programming interface (API) for browser extensions. While this particular work did not reach fruition, every major browser now has
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