Section: Scientific Foundations
Computer Virology
From an historical point of view, the first official virus appeared in 1983 on Vax-PDP 11. In the very same time, a series of papers was published which always remain a reference in computer virology: Thompson [105] , Cohen [61] and Adleman [44] .
The literature which explains and discusses practical issues is quite extensive, see for example Ludwig's book [86] or Szor's one [103] and all web sites...But, we think that the best references are both books of Filiol [65] (English translation [66] ) and [68] . However, there are only a few theoretical/scientific studies, which attempt to give a model of computer viruses.
A virus is essentially a self-replicating program inside an
adversary environment. Self-replication has a solid background
based on works on fixed point in 
-calculus and on
studies of Von Neumann [107] . More precisely we establish in [53]
that Kleene's second recursion theorem [83] is the
cornerstone from which viruses and infection scenarios can be defined
and classified. The bottom line of a virus is
behavior is
-
A virus infect programs by modifying them
-
A virus copies itself and can mutate
-
Virus spreads throughout a system
The above scientific foundation justifies our position to use the word virus as a generic word for self-replicating malwares. (There is yet a difference. A malware has a payload, and virus may not have one.) For example, worms are an autonous self-replicating malware and so fall into our definition. In fact, the current malware taxonomy (virus, worms, trojans, ...) is unclear and subject to debate.
