A computer virus is a computer program A computer program is a sequence of instructions written to perform a specified task for a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute the instructions. The same program in its human- that can copy itself[1] and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. The term "computer virus" is sometimes used as a catch-, adware Adware, or advertising-supported software, is any software package which automatically plays, displays, or downloads advertisements to a computer after. The object of the Adware is to generate revenue for its author. Adware, by itself, is harmless; however, some adware may come with integrated spyware such as keyloggers and other privacy-invasive, and spyware Spyware is a type of malware that can be installed on computers and collects little bits of information at a time about users without their knowledge. The presence of spyware is typically hidden from the user, and can be difficult to detect. Typically, spyware is secretly installed on the user's personal computer. Sometimes, however, spywares such programs that do not have the reproductive ability. A true virus can only spread from one computer to another (in some form of executable code A code is a rule for converting a piece of information into another form or representation (one sign into another sign), not necessarily of the same type) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell, CD A Compact Disc is an optical disc used to store digital data. It was originally developed to store sound recordings exclusively, but later it also allowed the preservation of other types of data. Audio CDs have been commercially available since October 1982. In 2010, they remain the standard physical storage medium for audio, DVD DVD, also known as Digital Video Disc or Digital Versatile Disc, is an optical disc storage media format, and was invented and developed by Philips, Sony, Toshiba, and Time Warner in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs , but are capable of storing just under seven times as much data, or USB drive A USB flash drive consists of a flash memory data storage device integrated with a USB 1.1 or 2.0 interface. USB flash drives are typically removable and rewritable, and much smaller than a floppy disk. Most weigh less than 30 g (1 oz). Storage capacities in 2010 can be as large as 256 GB with steady improvements in size and price per capacity. Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.[2][3]
As stated above, the term "computer virus" is sometimes used as a catch-all phrase to include all types of malware Malware, short for malicious software, is software designed to infiltrate a computer system without the owner's informed consent. The expression is a general term used by computer professionals to mean a variety of forms of hostile, intrusive, or annoying software or program code. The term "computer virus" is sometimes used as a catch-, adware Adware, or advertising-supported software, is any software package which automatically plays, displays, or downloads advertisements to a computer after. The object of the Adware is to generate revenue for its author. Adware, by itself, is harmless; however, some adware may come with integrated spyware such as keyloggers and other privacy-invasive, and spyware Spyware is a type of malware that can be installed on computers and collects little bits of information at a time about users without their knowledge. The presence of spyware is typically hidden from the user, and can be difficult to detect. Typically, spyware is secretly installed on the user's personal computer. Sometimes, however, spywares such programs that do not have the reproductive ability. Malware includes computer viruses, worms A computer worm is a self-replicating malware computer program. It uses a computer network to send copies of itself to other nodes and it may do so without any user intervention. This is due to security shortcomings on the target computer. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least, trojans A Trojan, sometimes referred to as a Trojan horse, is non-self-replicating malware that appears to perform a desirable function for the user but instead facilitates unauthorized access to the user's computer system. The term is derived from the Trojan Horse story in Greek mythology, most rootkits A rootkit is a collection of tools that enable administrator-level access to a computer or computer network. Typically, a cracker installs a rootkit on a computer after first obtaining user-level access, either by exploiting a known vulnerability or cracking a password. Once the rootkit is installed, it allows the attacker to mask intrusion and, spyware, dishonest adware, crimeware Crimeware is a class of malware designed specifically to automate cybercrime. The term was coined by Peter Cassidy, Secretary General of the Anti-Phishing Working Group to distinguish it from other kinds of malevolent programs.[citation needed], and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with computer worms A computer worm is a self-replicating Malware computer program. It uses a computer network to send copies of itself to other nodes and it may do so without any user intervention. This is due to security shortcomings on the target computer. Unlike a virus, it does not need to attach itself to an existing program. Worms almost always cause at least and Trojan horses A Trojan, sometimes referred to as a Trojan horse, is non-self-replicating malware that appears to perform a desirable function for the user but instead facilitates unauthorized access to the user's computer system. The term is derived from the Trojan Horse story in Greek mythology, which are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan is a program that appears harmless but hides malicious functions. Worms and Trojans, like viruses, may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious and go unnoticed.
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History
The Creeper virus was first detected on ARPANET ARPANET , created by a small research team at the head of the Massachusetts Institute of Technology and the Defense Advanced Research Projects Agency (DARPA) of the United States Department of Defense, was the world's first operational packet switching network, and one of the networks that came to compose the global Internet. The packet switching, the forerunner of the Internet The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and, in the early 1970s.[4] Creeper was an experimental self-replicating program written by Bob Thomas at BBN Technologies BBN Technologies is a high-technology company which provides research and development services. BBN is based next to Fresh Pond in Cambridge, Massachusetts, USA. It is perhaps best known for its work in the development of packet switching (including the ARPANET and the Internet) and for its 1978 acoustical analysis for the House Select Committee in 1971.[5] Creeper used the ARPANET to infect DEC PDP-10 The PDP-10 is a mainframe computer manufactured by Digital Equipment Corporation from the late 1960s on; the name stands for "Programmed Data Processor model 10". The first model was delivered in 1966. It was the machine that made time-sharing common; it looms large in hacker folklore because of its adoption in the 1970s by many computers running the TENEX operating system The TOPS-20 operating system by Digital Equipment Corporation was the second proprietary OS for the PDP-10 mainframe computer. TOPS-20 began in 1969 as Bolt, Beranek and Newman's TENEX operating system, using special paging hardware. The TOPS-20 system is almost entirely unrelated to the similarly-named TOPS-10, but it was shipped with the PA1050. Creeper gained access via the ARPANET and copied itself to the remote system where the message, "I'm the creeper, catch me if you can!" was displayed. The Reaper program was created to delete Creeper.[6]
A program called "Rother J" was the first computer virus to appear "in the wild" — that is, outside the single computer or lab where it was created.[7] Written in 1981 by Richard Skrenta, it attached itself to the Apple DOS Apple DOS refers to operating systems for the Apple II series of microcomputers from late 1978 through early 1983. Apple DOS had three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS 3.2 did that minor release receive its 3.3 operating system and spread via floppy disk A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell.[7][8] This virus, created as a practical joke when Skrenta was still in high school, was injected in a game on a floppy disk. On its 50th use the Elk Cloner virus would be activated, infecting the computer and displaying a short poem beginning "Elk Cloner: The program with a personality."
The first PC virus in the wild was a boot sector virus dubbed (c)Brain[9], created in 1986 by the Farooq Alvi Brothers in Lahore, Pakistan, reportedly to deter piracy of the software they had written[10]. However, analysts have claimed that the Ashar virus, a variant of Brain, possibly predated it based on code within the virus.[original research?]
Before computer networks became widespread, most viruses spread on removable media, particularly floppy disks A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangular plastic shell. In the early days of the personal computer A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe, many users regularly exchanged information and programs on floppies. Some viruses spread by infecting programs stored on these disks, while others installed themselves into the disk boot sector A boot sector is a sector of a hard disk, floppy disk, or similar data storage device that contains code for booting programs stored in other parts of the disk, ensuring that they would be run when the user booted the computer from the disk, usually inadvertently. PCs of the era would attempt to boot first from a floppy if one had been left in the drive. Until floppy disks fell out of use, this was the most successful infection strategy and boot sector viruses were the most common in the wild for many years.[11]
Traditional computer viruses emerged in the 1980s, driven by the spread of personal computers and the resultant increase in BBS A Bulletin Board System, or BBS, is a computer system running software that allows users to connect and log in to the system using a terminal program. Once logged in, a user can perform functions such as uploading and downloading software and data, reading news and bulletins, and exchanging messages with other users, either through electronic mail, modem A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog use, and software sharing. Bulletin board A bulletin board is a place where people can leave public messages, for example, to advertise things to buy or sell, announce events, or provide information. Bulletin boards are often made of a material such as cork to facilitate addition and removal of messages or it can be placed on the computer so people can leave and erase messages for other-driven software sharing contributed directly to the spread of Trojan horse programs, and viruses were written to infect popularly traded software. Shareware The term shareware refers to proprietary software that is provided to users without payment on a trial basis and is often limited by any combination of functionality, availability or convenience. Shareware is often offered as a download from an Internet website or as a compact disc included with a periodical such as a newspaper or magazine. The and bootleg Copyright infringement is the unauthorized or prohibited use of works covered by copyright law, in a way that violates one of the copyright owner's exclusive rights, such as the right to reproduce or perform the copyrighted work, or to make derivative works software were equally common vectors for viruses on BBS's.[citation needed] Within the "pirate scene" of hobbyists trading illicit copies of retail software Retail software is computer software sold to end consumers, usually under restricted licenses. Until the emergence of the Internet, retail software represented, until the 2000s, the vast majority of all end consumer software used and was referred to as shrinkware because software almost always ships in a shrinkwrapped box. An important historical, traders in a hurry to obtain the latest applications were easy targets for viruses.[original research?]
Macro viruses have become common since the mid-1990s. Most of these viruses are written in the scripting languages for Microsoft programs such as Word Microsoft Word is a word processor designed by Microsoft. It was first released in 1983 under the name Multi-Tool Word for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS , the Apple Macintosh (1984), the AT&T Unix PC (1985), Atari ST (1986), SCO UNIX, OS/2, and Microsoft Windows ( and Excel Microsoft Excel is a spreadsheet application written and distributed by Microsoft for Microsoft Windows and Mac OS X. It features calculation, graphing tools, pivot tables and a macro programming language called VBA (Visual Basic for Applications). It has been the most widely used spreadsheet application available for these platforms since version and spread throughout Microsoft Office Microsoft Office is an office suite of interrelated desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems. Microsoft Office was introduced by Microsoft in 1989 for Macintosh, with a version for Windows in 1990. Initially a marketing term for a bundled set of applications, the first version of Office by infecting documents and spreadsheets. Since Word and Excel were also available for Mac OS Mac OS is the trademark-protected name for a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface. The original form of what Apple would later name the "Mac OS" was the, most could also spread to Macintosh computers The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a graphical user interface rather than a command-line interface. The company continued. Although most of these viruses did not have the ability to send infected e-mail Electronic mail, most commonly abbreviated email or e-mail, is a method of exchanging digital messages. E-mail systems are based on a store-and-forward model in which e-mail server computer systems accept, forward, deliver and store messages on behalf of users, who only need to connect to the e-mail infrastructure, typically an e-mail server, with, those viruses which did took advantage of the Microsoft Outlook Microsoft Outlook, formerly Microsoft Office Outlook, is a personal information manager from Microsoft. The 2007 version is available both as a separate application as well as a part of the Microsoft Office suite. The current versions are Microsoft Office Outlook 2007 for Windows and in late 2009, Microsoft released the beta version of Microsoft COM Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages. The term COM is often used in the Microsoft software development industry as an umbrella term that encompasses the OLE, interface.[citation needed]
Some old versions of Microsoft Word allow macros to replicate themselves with additional blank lines. If two macro viruses simultaneously infect a document, the combination of the two, if also self-replicating, can appear as a "mating" of the two and would likely be detected as a virus unique from the "parents".[12]
A virus may also send a web address In computing, a Uniform Resource Locator is a Uniform Resource Identifier (URI) that specifies where an identified resource is available and the mechanism for retrieving it. In popular usage and in many technical documents and verbal discussions it is often incorrectly used as a synonym for URI,. The best-known example of a URL is the " link as an instant message Instant messaging is a form of real-time communication between two or more people based on typed text. The text is conveyed via devices connected over a network such as the Internet to all the contacts on an infected machine. If the recipient, thinking the link is from a friend (a trusted source) follows the link to the website, the virus hosted at the site may be able to infect this new computer and continue propagating.
Viruses that spread using cross-site scripting Cross-site scripting is a type of computer security vulnerability typically found in web applications that enables malicious attackers to inject client-side script into web pages viewed by other users. An exploited cross-site scripting vulnerability can be used by attackers to bypass access controls such as the same origin policy. Cross-site were first reported in 2002[13], and were academically demonstrated in 2005.[14] There have been multiple instances of the cross-site scripting viruses in the wild, exploiting websites such as MySpace Samy was an XSS Worm developed to propagate across the MySpace social-networking site. At the time of release it gained significant media attention and Yahoo Yahoo! Inc. is an American public corporation headquartered in Sunnyvale, California, (in Silicon Valley), that provides Internet services worldwide. The company is perhaps best known for its web portal, search engine (Yahoo! Search), Yahoo! Directory, Yahoo! Mail, Yahoo! News, advertising, online mapping (Yahoo! Maps), video sharing (Yahoo! Video).
Infection strategies
In order to replicate itself, a virus must be permitted to execute code and write to memory. For this reason, many viruses attach themselves to executable files that may be part of legitimate programs. If a user attempts to launch an infected program, the virus' code may be executed simultaneously. Viruses can be divided into two types based on their behavior when they are executed. Nonresident viruses immediately search for other hosts that can be infected, infect those targets, and finally transfer control to the application program Application software, also known as applications or apps, is computer software designed to help the user to perform singular or multiple related specific tasks. Examples include Enterprise software, Accounting software, Office suites, Graphics software and media players they infected. Resident viruses do not search for hosts when they are started. Instead, a resident virus loads itself into memory on execution and transfers control to the host program. The virus stays active in the background and infects new hosts when those files are accessed by other programs or the operating system itself.
Nonresident viruses
Nonresident viruses can be thought of as consisting of a finder module and a replication module. The finder module is responsible for finding new files to infect. For each new executable file the finder module encounters, it calls the replication module to infect that file.
Resident viruses
Resident viruses contain a replication module that is similar to the one that is employed by nonresident viruses. This module, however, is not called by a finder module. The virus loads the replication module into memory when it is executed instead and ensures that this module is executed each time the operating system is called to perform a certain operation. The replication module can be called, for example, each time the operating system executes a file. In this case the virus infects every suitable program that is executed on the computer.
Resident viruses are sometimes subdivided into a category of fast infectors and a category of slow infectors. Fast infectors are designed to infect as many files as possible. A fast infector, for instance, can infect every potential host file that is accessed. This poses a special problem when using anti-virus software, since a virus scanner will access every potential host file on a computer when it performs a system-wide scan. If the virus scanner fails to notice that such a virus is present in memory the virus can "piggy-back" on the virus scanner and in this way infect all files that are scanned. Fast infectors rely on their fast infection rate to spread. The disadvantage of this method is that infecting many files may make detection more likely, because the virus may slow down a computer or perform many suspicious actions that can be noticed by anti-virus software. Slow infectors, on the other hand, are designed to infect hosts infrequently. Some slow infectors, for instance, only infect files when they are copied. Slow infectors are designed to avoid detection by limiting their actions: they are less likely to slow down a computer noticeably and will, at most, infrequently trigger anti-virus software that detects suspicious behavior by programs. The slow infector approach, however, does not seem very successful.
Dark Reading
... door-to-door collections, mailings and telephone calls, and similar methods. contained within those messages because they may contain computer viruses . ...
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Your computers hidden folders cannot be accessed even after changing the folder settings There are several scvhost exe processes running simultaneously and should not be confused with the
