My Broadcast

Barry Shein (
Mon, 6 Apr 87 15:29:03 EDT

>From Dennis Perry:
>I would like suggestions as to what you, or anyone else, think should be
>done to prevent such occurances in the furture.


Edit /etc/servers and remove the rwalld line. This will disable the
remote service. The local "write to all users" program, 'wall', can
still be used on any individual system. To shout to all systems in an
area either have the operators log in and run wall locally or execute
it via 'rsh system wall ..msg..' from a locally trusted site (as per
the rsh restrictions.) A command file could be created trivially which
simulated "rwall" to a selected set of sites:

echo "Enter message to be sent to all systems (one line)"
echo -n 'MESSAGE: '
read msg
for i in host1 host2 etc...
        rsh $i wall $msg

(I didn't test this, but I think the point is clear.)

This can be further enhanced by removing the rwall binary from your
systems, but if you don't support the daemon, you're not going to see
any broadcasts, so it's under your control. Done.

        -Barry Shein, Boston University

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