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X-issue: 4.36
From: hplabs!pyramid!utzoo!henry@ucbvax.Berkeley.EDU
Date: Tue, 6 Jan 87 16:53:46 pst
Subject: Risks Involved in Campus Network-building

It can get worse.  Consider someone who is angry at the administration,
perhaps having just flunked out, been expelled, or whatever.  There is
some sophistication involved in doing things like watching the network
for passwords etc.  There is little or no sophistication needed to just
run some copper between the network cable and a 110V wall socket.  Not
only does this disrupt the network, it probably destroys a great deal of
equipment, and creates a serious safety hazard.  Good luck identifying
the culprit, too!  In most networking setups this would probably be
utterly untraceable once the connection was broken.

I see reason for worry about newer, cheaper local-networking schemes that
tend to run the network cable itself onto a board on each computer's
backplane.  Traditional thick-wire Ethernet is costly, but its transceivers
do provide thousands of volts of isolation between network and computer.
A disastrous fault on the network will only destroy transceivers.  Fiber
networks likewise provide inherent isolation.

The same problem exists, on a more modest scale, with existing setups
involving RS232 cables.  There the wiring is (probably) not a shared
resource, but the electronics on the other end are.  If your computer
facility casually runs RS232 cabling all over the building (as we do),
remember that this means your computer is plugged into a net of wire
with exposed pins in all kinds of places.  RS232 interfaces are seldom
opto-isolated, which is what would be needed to defend against electrical
flaws in such setups.

That net of wiring also makes a dandy lightning antenna.  That's one
reason, by the way, why a separate-box modem is almost always a better
idea than one that plugs into a backplane slot -- more isolation between
phone line and computer.
				Henry Spencer @ U of Toronto Zoology

     [Thanks.  Enough on this topic for now?  We seem to have plateued.  PGN]

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