From: John Beckett 

"Geo."  wrote in message
news::
> that's what they are but how do they work?

My understanding of this is very likely lower than Alan's, but I will
nevertheless suggest a "high level" explanation for how viruses
work.

A cell is a self-sufficient package (requiring certain inputs) that can
reproduce by division.

A virus is something that takes advantage of the machinery in certain
cells. The virus can enter the cell, then subvert the cell's reproduction
tools to reproduce the virus. The cell bursts when too many viruses have
been created. The freed viruses then drift around, ready to repeat this
process on any other similar cells.

I realise this is not the kind of explanation you had in mind. However, it
is satisfying in another way: Given that a cell can reproduce, anything
that can (1) enter the cell, and (2) trigger the reproduction mechanism
will propagate itself.

Cells have security mechanisms to block (1), but if they don't have the
latest service pack, they are vulnerable!

John

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