<P> The term "virus" is also commonly, but erroneously, used to refer to other types of malware . "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 majority of active malware threats are actually trojan horse programs or computer worms rather than computer viruses . The term computer virus, coined by Fred Cohen in 1985, is a misnomer . 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 private information (e.g., credit card numbers), corrupting data, displaying political or humorous messages on the user's screen, spamming their e-mail contacts, logging their keystrokes, or even rendering the computer useless . However, not all viruses carry a destructive "payload" and attempt to hide themselves--the defining characteristic of viruses is that they are self - replicating computer programs which modify other software without user consent . </P> <P> The first academic work on the theory of self - replicating computer programs was done in 1949 by John von Neumann who gave lectures at the University of Illinois about the "Theory and Organization of Complicated Automata". The work of von Neumann was later published as the "Theory of self - reproducing automata". In his essay von Neumann described how a computer program could be designed to reproduce itself . Von Neumann's design for a self - reproducing computer program is considered the world's first computer virus, and he is considered to be the theoretical "father" of computer virology . 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). The article describes a fully functional virus written in assembler programming language for a SIEMENS 4004 / 35 computer system . In 1980 Jürgen Kraus wrote his diplom thesis "Selbstreproduktion bei Programmen" (Self - reproduction of programs) at the University of Dortmund . In his work Kraus postulated that computer programs can behave in a way similar to biological viruses . </P> <P> The Creeper virus was first detected on ARPANET, the forerunner of the Internet, in the early 1970s . Creeper was an experimental self - replicating program written by Bob Thomas at BBN Technologies in 1971 . Creeper used the ARPANET to infect DEC PDP - 10 computers running the TENEX operating system . 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 . In fiction, 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 . Alan Oppenheimer's character summarizes the problem by stating that "...there's a clear pattern here which suggests an analogy to an infectious disease process, spreading from one...area to the next ." To which the replies are stated: "Perhaps there are superficial similarities to disease" and, "I must confess I find it difficult to believe in a disease of machinery ." </P> <P> 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 . Written in 1981 by Richard Skrenta while in the ninth grade at Mount Lebanon High School near Pittsburgh, it attached itself to the Apple DOS 3.3 operating system and spread via floppy disk . 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 personal computer and displaying a short poem beginning "Elk Cloner: The program with a personality ." In 1984 Fred Cohen from the University of Southern California wrote his paper "Computer Viruses--Theory and Experiments". It was the first paper to explicitly call a self - reproducing program a "virus", a term introduced by Cohen's mentor Leonard Adleman . In 1987, Fred Cohen published a demonstration that there is no algorithm that can perfectly detect all possible viruses . Fred Cohen's theoretical compression virus was an example of a virus which was not malicious software (malware), but was putatively benevolent (well - intentioned). However, antivirus professionals do not accept the concept of "benevolent viruses", as any desired function can be implemented without involving a virus (automatic compression, for instance, is available under the Windows operating system at the choice of the user). Any virus will by definition make unauthorised changes to a computer, which is undesirable even if no damage is done or intended . On page one of Dr Solomon's Virus Encyclopaedia, the undesirability of viruses, even those that do nothing but reproduce, is thoroughly explained . </P>

Which was the first virus detected by arpanet