Computer virus - Definition

In computer security technology, a virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents. A computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells. Extending the analogy, the insertion of a virus into the program is termed as an infection, and the infected file (or executable code that is not part of a file) is called a host. Viruses are one of the several types of malicious software or malware. In ...

Including:

• Computer virus - Definition
• Computer virus - Use of the word virus
• Computer virus - History
• Computer virus - Why people create computer viruses
• Computer virus - Replication Strategies
• Computer virus - Nonresident viruses
• Computer virus - Resident viruses
• Computer virus - Host types
• Computer virus - Methods to avoid detection
• Computer virus - Avoiding bait files and other undesirable hosts
• Computer virus - Stealth
• Computer virus - Self-modification
• Computer virus - Viruses and legitimate software
• Computer virus - The vulnerability of operating systems to viruses
• Computer virus - The role of software development
• Computer virus - Anti-virus software and other countermeasures

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A virus is a type of program that can replicate itself by making (possibly modified) copies of itself. The main criterion for classifying a piece of executable code as a virus is that it spreads itself by means of 'hosts'. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable medium. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Definition

A virus is a type of program that can replicate itself by making (possibly modified) copies of itself. The main criterion for classifying a piece of executable code as a virus is that it spreads itself by means of 'hosts'. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable media. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by a ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Definition

In order to avoid detection by users, some viruses employ different kinds of obfuscation. Some old viruses, especially on the MS-DOS platform, make sure that the "last modified" date of a host file stays the same when the file is infected by the virus. This approach does not fool anti-virus software, however. Some viruses can infect files without increasing their sizes or damaging the files. They accomplish this by overwriting unused areas of executable files. These are called cavity viruses. For example the CIH virus, or Chern ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Methods to avoid detection

Computer virus - The vulnerability of operating systems to viruses. Another analogy to biological viruses: just as genetic diversity in a population decreases the chance of a single disease wiping out a population, the diversity of software systems on a network similarly limits the destructive potential of viruses. This became a particular concern in the 1990s, when Microsoft gained market dominance in desktop operating systems and office suites. Users who use Microsoft software (especially networking soft ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Viruses and legitimate software

Unlike biological viruses, computer viruses do not simply evolve by themselves, except in the cases where copying errors and recombination have led to actual evolution of computer viruses; however, these cases are very rare compared to the rapid generation of new malware by human programmers. They cannot come into existence spontaneously, nor can they be created by bugs in regular programs. They are deliberately ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Why people create computer viruses

The term "virus" was first used in an academic publication by Fred Cohen in his 1984 paper Experiments with Computer Viruses, where he credits Len Adleman with coining it. However, a 1972 science fiction novel by David Gerrold, When H.A.R.L.I.E. Was One, includes a description of a fictional computer program called "VIRUS" that worked just like a virus (and was countered by a program called "ANTIBODY"); and John Brunner's 1975 novel The Shockwave Rider describes programs known as "tapeworms" which spread through a networ ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Use of the word virus

A program called "Elk Cloner" is credited with being the first computer virus to appear "in the wild" -- that is, outside the single computer or lab where it was created. Written in 1982 by Rich Skrenta, it attached itself to the Apple DOS 3.3 operating system and spread by floppy disk. The first PC virus was a boot sector virus called (c)Brain, created in 1986 by two brothers, Basit and Amjad Farooq Alvi, operating out of Lahore, Pakistan. The brothers reportedly created the virus to deter pirated copies of software they had written.[1] However, analysts have claimed that the Ashar virus, a variant of Brain, possibly p ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - History

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 tries to start an infected program, the virus' code may be executed first. Viruses can be divided into two types, on the basis of their behavior when they get executed. Nonresident viruses immediately search for other hosts that can be infected, infect these targets, and finally transfer control to the application program they infect ...

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Computer virus, Computer virus - Definition, Computer virus - Use of the word virus, Computer virus - History, Computer virus - Why people create computer viruses, Computer virus - Replication Strategies, Computer virus - Nonresident viruses, Computer virus - Resident viruses, Computer virus - Host types, Computer virus - Methods to avoid detection, Computer virus - Avoiding bait files and other undesirable hosts, Computer virus - Stealth, Computer virus - Self-modification, Computer virus - Viruses and legitimate software, Computer virus - The vulnerability of operating systems to viruses, Computer virus - The role of software development, Computer virus - Anti-virus software and other countermeasures

Read more here: » Computer virus: Encyclopedia II - Computer virus - Replication Strategies