there are 2 answers to this question, depending on whether you're using the natural language definition or the mathematical definition used in logical proofs...
natural language definition
a virus is self-replicating program that attaches a (possibly evolved) copy of itself to other (host) programs in such a way that when an attempt is made to run the host program a call may be made to run the copy of the virus instead of or as well as the original host program...
the attachment mentioned above is commonly referred to as infection... usually it infers that a copy of the virus is actually placed within the host, however this is not always the case... the only real requirements for the attachment are spelled out above...
mathematical definition
the mathematical definition in it's most simplistic natural language form is - a virus is a self-replicating program...
this may seem a little odd that no mention of infection is made at all, but for infection to occur you need to have the concept of separate and distinguishable programs and that doesn't exist in the context in which the mathematical definition is used... it applies to the turing machine model of computation and a turing machine makes no distinction between different sets of symbols on it's tape... without logical partitions between different sets of symbols there can be no separate programs and therefore no specific host program to infect... at most the definition specifies that any offspring of the virus must not overlap the original instance of the virus (or in other words it must not overwrite the original virus in part or in full)...
(see section 3 of this paper for a more precise retelling of the formal virus definition)
back to index
0 comments:
Post a Comment