Computer viruses are called "viruses" because, like their biological counterparts, they had the ability to self-propagation. KOH also has this ability, therefore it's a virus (or a compound which includes a virus component)"
In this case DOS is also a virus (or a compound which includes a virus component), because it has the SYS and COPY commands. And if the boot disk has the AUTOEXEC.BAT file similar to the one shown above, there is even no need for a user to initiate the propagation process. In addition to that, if we consider the capability to self-propagate to be a necessary and sufficient feature of a virus, that every software which includes an installation program is a virus. Therefore this argument fails.
- .. what if we define a virus as not just "self propagating code", but "self propagating code not doing anything useful and even doing harm, without user participation or even noticing"...
The KOH virus is a program encrypting disks using a password supplied by user. Everything it does is being commented on the display and all the actions are confirmed by the user. In addition to that it also has the "uninstall" option to it that decrypts all the disks and deletes the program body. Nevertheless it's a virus!
Judging by subjective criteria in case of ALREADY.COM (useful/useless, it's part of a compound/is a stand-alone etc.) maybe it is incorrect to call it a virus/worm. But what's the use being subjective?
But what can objective criteria of being a virus be? Might that be self propagation, obscurity, destructive capabilities? But for each objective criterion one might find 2 counter examples - a) some particular virus not meeting this criterion, and b) some particular non-virus program meeting this criterion:
Self propagation:
a. intended viruses, which can not propagate because of numerous errors, or propagate under very limited conditions.
b. MS-DOS and variations of SYS+COPY.
Obscurity:
a. "KOH", "VirDemo", "Macro.Word.Polite" viruses and some others inform user about their presence and propagation.
b. how many drivers counting by tens do Microsoft Windows95 load? They're all obscure by the way.
Destructive capabilities:
a. harmless viruses like "Yankee", who feel fine under DOS, Windows 3.x, Windows95, NT and don't mess up anything.
b. the older versions of Norton Disk Doctor applied to drives with long filenames. In this case Disk Doctor turns out to be Disk Destroyer.
And so the question whether it is possible to give "normal" definition of computer virus is still open.