You probably think that you are running Antivirus Software. It’s a very common conception.
This drives those of us on this side of the fence a little batty. You see, inside the AV industry we have been detecting things other than viruses and using methods that aren’t exactly what you think since the very beginning. Not only that but from a specific insider perspective, words like virus, Trojan, worm, and malware all have very specific and exact meanings. I really don’t care if you call everything a virus, but when I use the word I mean something specific. So I thought we might start this blog with some definitions and explanations. Here goes.
Virus—the term was invented by Fred Cohen’s grad advisor in the early 1980’s. Fred published his dissertation, A Short Course on Computer Viruses in 1985. There had been viruses for a while but they weren’t yet called that. So what is a virus? To quote Dr Cohen:
When we talk about computer viruses in the deepest sense we are talking about sequences of symbols in the memory of a machine in whatever form that may be, main memory, the registers, disk, tape, or what have you.—-Most of the viruses you have probably heard about form singleton viral sets (e.g., sequences of instructions in machine code for the particular machine that make exact copies of themselves somewhere else in the machine)
Having gotten that over, I promise to never again quote a doctoral dissertation in this blog again. I just wanted you to know that I had a signed copy of it right here on my bookshelf, and knew where the term came from.
In short, viruses replicate. They make copies of themselves. There are no viruses that don’t replicate. It doesn’t have to be destructive to be a virus (in fact, almost none of them are destructive) nor does it have to interact with you the user, or do anything you can actually see. Viruses replicate.
Now this is serious business. What makes a difference between a virus and the other kinds of malware. (malware being the umbrella term that covers all of the malicious and unwanted software on your system) is that a virus, once it has infected you, will hang around and try to infect others, too.
David Perry's Blog 
addenda: Fred Cohen wanted to write about “Self replicating cellular automata” after the thought experiments of Hungarian mathematician John Von Neumann. I don’t think it would fit on the box as well. I use the word virus in the title of this blog as a call to attention, then do my best to educate.
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However, no-one outside the computer security business gives a flying fig about whether something is a virus, a trojan, a phishing attack, an exploit, or a hole in the ground. And they shouldn’t have to. I have no idea whether whatever’s wrong with my car is faulty electronics, faulty mechanics, faulty hoses or anything else, nor do I care – I just want it fixed.
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Good point, Pat. I did tech support for 26 years, half of that in the antivirus field. I absolutely both agree and disagree with what you say. It’s true that they don’t care what the exact problem is, but the average user is way off base for what they are risking, what the problem actually is, where the threat comes from and so on. There is both a mis placed fear of things that don’t exist and a genuine denial of the the real problems (which are myriad) I am getting there in baby steps. Please bear with me for a while. I don’t think I am wasting anyone’s time.
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