Virus Reference 2.1.6 mentions an 'Unnamed PostScript hack' which
disables PostScript printers and requires replacement of a chip on
the printer logic board to repair. A Mac virus guru says:
"The PostScript 'Trojan' was basically a PostScript job that
toggled the printer password to some random string a number of
times. Some Apple laser printers have a firmware counter that
allows the password to only be changed a set number of times
(because of PRAM behavior or licensing -- I don't remember which),
so eventually the password would get "stuck" at some random string
that the user would not know. I have not heard any reports of
anyone suffering from this in many years."