Archived viruses, was Re: Reasonable price for a complete SOL-20 system?

Sean Conner spc at
Mon Oct 24 16:00:12 CDT 2016

It was thus said that the Great allison once stated:
> On 10/23/2016 09:15 PM, Mouse wrote:
> >> My favorite formatter was my S100 crate with CP/M, [it's] impossible
> >> to give a single user OS without background processing a virus.
> > I disagree.  I see nothing about "a single-user OS without background
> > processing" that would prevent a virus from infecting other programs,
> > even including the OS, when it's run, and potentially doing something
> > else as well.
> >
> > Perhaps you are using some meaning of "virus" other than "piece of
> > software that infects other software to propagate itself"?  That's the
> > only meaning that makes any sense to me.
> >
> Its highly unlikely as first it would have to install itself and do so
> without corrupting the OS. CP/M-80 is a machine monitor with a file system
> and lacking most of the usual read the disk and "do something" automation. 
> The only automation in CP/M is logging a drive which is reading the
> directory and mapping used blocks. So the initial load would have to be
> performed by the user.  Trogan maybe, social engineered for sure, virus
> no.  The key is you have to actually execute a file for action to happen. 
> In CP/M you can disk dump sectors and never execute them, formatting is
> even more benign, the disk is never read save for a post format verify.

  MS-DOS had CP/M at its heart, and it had its fair share of virii (viruses? 
What is the plural of a computer virus?).  The discussion Liam linked to
(!topic/comp.os.cpm/V1-zYzA6Uzg) seems to
echo my own thoughts here---technically, it's possible, but not probable due
to the resource constraints (mainly memory) inherent in CP/M.  There is
nothing that also requires a virus to run a background process---it can
certainly modify the existing program to infect other programs, but again,
on CP/M because of the contrained resources (and lack of speed) such actions
might be noticed by the user.

  And in my experience [1] most viruses would infect executable programs and
it wasn't until Windows, when Microsoft went out of its way to find any form
of code in any file type and execute it, did viruses start infecting other
types of files (at first, I didn't believe reports of viruses spreading via
JPEGs, but yup, it was true.  Thanks, Microsoft!).


[1]	Never got any in my day-to-day activities, but there was an outbreak
	at the university I attended in the late 80s.  I managed to snag an
	example and decompile it.  I have no idea what virus it was, but I
	think I still have a copy in my floppy archives somewhere.

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