Computer virus

virusvirusescomputer virusesboot sector virusstealthvirus signatureBoot virusComputer VirologyEmail virusemail viruses
A computer virus is a type of computer program that, when executed, replicates itself by modifying other computer programs and inserting its own code.wikipedia
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Malware

malicious softwaremalicious codemalicious
The term "virus" is also misused by extension to refer to other types of malware. Fred Cohen's theoretical compression virus was an example of a virus which was not malicious software (malware), but was putatively benevolent (well-intentioned).
A wide variety of types of malware exist, including computer viruses, worms, Trojan horses, ransomware, spyware, adware, and scareware.

Computer worm

wormswormComputer worms
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software.
Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.

Spyware

anti-spywareantispywareSpyware removal software
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software.
Spyware does not necessarily spread in the same way as a virus or worm because infected systems generally do not attempt to transmit or copy the software to other computers.

Rootkit

rootkitsbootkitantirootkit
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software.
The first documented computer virus to target the personal computer, discovered in 1986, used cloaking techniques to hide itself: the Brain virus intercepted attempts to read the boot sector, and redirected these to elsewhere on the disk, where a copy of the original boot sector was kept.

Self-replication

self-replicatingreplicationreplicate
In 1972, Veith Risak directly building on von Neumann's work on self-replication, published his article "Selbstreproduzierende Automaten mit minimaler Informationsübertragung" (Self-reproducing automata with minimal information exchange).
Computer viruses reproduce using the hardware and software already present on computers.

Gregory Benford

Greg BenfordBenford's law of controversyA Dance to Strange Musics
The first known description of a self-reproducing program in a short story occurs in a 1970 story by Gregory Benford which describes a computer program called VIRUS which, when installed on a computer with telephone modem dialling capability, randomly dials phone numbers until it hit a modem that is answered by another computer.
In 1969 he wrote "The Scarred Man", the first story about a computer virus, published in 1970.

Fred Cohen

Frederick B. Cohen
The term computer virus, coined by Fred Cohen in 1985, is a misnomer.
Frederick B. Cohen (born 1956) is an American computer scientist and best known as the inventor of computer virus defense techniques.

Trojan horse (computing)

Trojan horsetrojanTrojan horses
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software.
Unlike computer viruses and worms, Trojans generally do not attempt to inject themselves into other files or otherwise propagate themselves.

John Brunner (novelist)

John BrunnerBedlam PlanetBrunner, John
The idea was explored further in two 1972 novels, When HARLIE Was One by David Gerrold and The Terminal Man by Michael Crichton, and became a major theme of the 1975 novel The Shockwave Rider by John Brunner.
Brunner is credited with coining the term "worm" and predicting the emergence of computer viruses in his 1975 novel The Shockwave Rider, in which he used the term to describe software which reproduces itself across a computer network.

Elk Cloner

In 1982, a program called "Elk Cloner" was the first personal computer virus to appear "in the wild"—that is, outside the single computer or [computer] lab where it was created.
Elk Cloner is one of the first known microcomputer viruses that spread "in the wild", i.e., outside the computer system or laboratory in which it was written.

Email spam

spame-mail spamspam email
Viruses often perform some type of harmful activity on infected host computers, such as acquisition of hard disk space or central processing unit (CPU) time, accessing and stealing private information (e.g., credit card numbers, Debit card numbers, phone numbers, names, email addresses, passwords, Bank Information, House Addresses, etc), corrupting data, displaying political, humorous or threatening messages on the user's screen, spamming their e-mail contacts, logging their keystrokes, or even rendering the computer useless.
Backscatter is a side-effect of email spam, viruses, and worms.

Brain (computer virus)

Brain(c)BrainAmjad Farooq Alvi
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 Lahore, Pakistan, reportedly to deter unauthorized copying of the software they had written.
Brain is the industry standard name for a computer virus that was released in its first form in January 1986, and is considered to be the first computer virus for MS-DOS.

Compression virus

Fred Cohen's theoretical compression virus was an example of a virus which was not malicious software (malware), but was putatively benevolent (well-intentioned).
A compression virus is an example of a benevolent computer virus, invented by Fred Cohen.

Westworld (film)

Westworld1973 film of the same name1973 science fiction Western thriller of the same name
The 1973 Michael Crichton sci-fi movie Westworld made an early mention of the concept of a computer virus, being a central plot theme that causes androids to run amok.
The technicians running Delos notice problems beginning to spread like an infection among the androids: the androids in Romanworld and Medievalworld begin experiencing an increasing number of breakdowns and systemic failures, which are said to have spread to Westworld.

Virus hoax

computer virus hoaxcomputer virus hoaxesfraudulent virus warning
Payload activity might be noticeable (e.g., because it causes the system to slow down or "freeze"), as most of the time the "payload" itself is the harmful activity, or some times non-destructive but distributive, which is called Virus hoax.
A computer virus hoax is a message warning the recipients of a non-existent computer virus threat.

Logic bomb

logic bombscode bomblogicbomb
The trigger, which is also known as a logic bomb, is the compiled version that could be activated any time within an executable file when the virus is run that determines the event or condition for the malicious "payload" to be activated or delivered such as a particular date, a particular time, particular presence of another program, capacity of the disk exceeding some limit, or a double-click that opens a particular file.
Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time or when some other condition is met.

Keystroke logging

keyloggerkeyloggerskeystroke logger
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software. Viruses often perform some type of harmful activity on infected host computers, such as acquisition of hard disk space or central processing unit (CPU) time, accessing and stealing private information (e.g., credit card numbers, Debit card numbers, phone numbers, names, email addresses, passwords, Bank Information, House Addresses, etc), corrupting data, displaying political, humorous or threatening messages on the user's screen, spamming their e-mail contacts, logging their keystrokes, or even rendering the computer useless.
Writing simple software applications for keylogging can be trivial, and like any nefarious computer program, can be distributed as a trojan horse or as part of a virus.

CIH (computer virus)

CIHCIH virusChen Ing Hau
For example, the CIH virus, or Chernobyl Virus, infects Portable Executable files.
CIH, also known as Chernobyl or Spacefiller, is a Microsoft Windows 9x computer virus which first emerged in 1998.

Science fiction

sci-fiscience-fictionSci Fi
The 1973 Michael Crichton sci-fi movie Westworld made an early mention of the concept of a computer virus, being a central plot theme that causes androids to run amok.
The animated series The Jetsons, while intended as comedy and only running for one season (1962–1963), predicted many inventions now in common use: flat-screen televisions, newspapers on a computer-like screen, computer viruses, video chat, tanning beds, home treadmills, and more.

COM file

COM.COM.COM files
One manner of classifying viruses is to analyze whether they reside in binary executables (such as .EXE or .COM files), data files (such as Microsoft Word documents or PDF files), or in the boot sector of the host's hard drive (or some combination of all of these).
However, this similarity in name has been exploited by malicious computer virus writers.

Payload (computing)

payloadpayload datapayloads
The "payload" is the actual body or data that performs the actual malicious purpose of the virus.
In the context of a computer virus or worm, the payload is the portion of the malware which performs malicious action.

Adware

ad-supportedad-sponsoredAd-supported software
"Malware" encompasses computer viruses along with many other forms of malicious software, such as computer "worms", ransomware, spyware, adware, trojan horses, keyloggers, rootkits, bootkits, malicious Browser Helper Object (BHOs), and other malicious software.
While some sources rate adware only as an "irritant", others classify it as an "online threat" or even rate it as seriously as computer viruses and trojans.

Denial-of-service attack

DDoSdenial of servicedistributed denial of service
Motives for creating viruses can include seeking profit (e.g., with ransomware), desire to send a political message, personal amusement, to demonstrate that a vulnerability exists in software, for sabotage and denial of service, or simply because they wish to explore cybersecurity issues, artificial life and evolutionary algorithms.
Many sites' servers thought the requests were from a virus or spyware trying to cause a denial-of-service attack, warning users that their queries looked like "automated requests from a computer virus or spyware application".

David Gerrold

The idea was explored further in two 1972 novels, When HARLIE Was One by David Gerrold and The Terminal Man by Michael Crichton, and became a major theme of the 1975 novel The Shockwave Rider by John Brunner.
This novel is notable for being one of the first to describe a computer virus.

Macro (computer science)

macromacrosmacro language
Many common applications, such as Microsoft Outlook and Microsoft Word, allow macro programs to be embedded in documents or emails, so that the programs may be run automatically when the document is opened.
This makes it relatively easy to write computer viruses in VBA, commonly known as macro viruses.