Bob Hayden wrote:
>
> I checked with a nerdy geek and was told that it is a waste of
> bandwidth to broadcast attachments to an entire mailing list.
This to some extend depends on the size of the attachment;
but the principle is sound UNLESS the list is a specialized one of
a nature that makes the use of attachments customary.
> Although not every attachment is a virus, NO ASCII text is.
I believe this is more or less true at the moment. However,
there was some speculation in the days of DOS that the "ANSI escape
sequences" that were used to do things like change color of text on
screen could be used to create a Trojan horse - although the writer
would need an IQ of 2n to write one that would fool a user with IQ n.
Here's the gimmick. The ANSI escape sequences did not just change text
and background color - they also moved the cursor. Once the programmers
were thinking about the keyboard, somebody had the idea of including a
(rarely-used) ANSI escape sequence to allow the keys to be remapped (to
facilitate international ckeyboard layouts, I supppose.) To make things
like dead accent keys work here, they allowed a key to be remapped to
more than one character. Being true programmers of the old school, they
did not limit this to the two or three characters that anybody actually
needed.
RESULT: You could in principle insert (undisplayed) ANSI escape
sequences into an arbitrary text string that would map the ENTER key to
"FORMAT C:", set several other keys to "Y", and make the display
black-on-black from the cursor point onwards. Somebody impetuous enough
to react to an apparently stuck display by hammering keys at random
might actually not only initiate the command to erase their hard drive
but also
"verify that this was what they wanted". This sort of thing was
actually tested, according to a 1990-vintage virus protection book I
used to have. The solution was a modified ANSI.SYS file that did not
support key remapping, or limited the length of the remapped string. I
used to have one of these on my machine.
It has been conjectured that a truly brilliant writer of short
assembler code might have been able to load and run a .com executable in
this fashion, from a text string. Remember, a program is just a string
of
characters - especially a .com which has very little "rubric" at the
head.
In principle you can create a program with a word processor if it does
not use one of a few truly unprintable characters. However, AFAIK this
was never successfully done.
The moral is that anything can be a virus if there is something to run
it. Code doesn't just run itself. Of course, this is true of
executables as well - an executable only runs when the OS puts it into
the CPU.
-Robert Dawson
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