That's not how a printer with a fax/modem works.

If the printer endpoint of the USB device receives a file that orders millions of pizzas, it will print the file (or print a PS error, or print the plaintext contents of the file), not order pizzas.

If the user mistakenly "prints" to the fax device, the file will be printed at the destination fax machine, at the number the user typed, not the number in the file, and it will print, not order pizzas (unless the pizzeria accepts fax orders, which would be a prank, not an attack).

> That's not how a printer with a fax/modem works.

It is how at least one of them works, and how I assumed all of them work. http://www.whoopis.com/howtos/laserwriter16-600/LaserWriter_...:

“FaxOptions Dictionary This dictionary contains parameters that direct fax transmissions from a PostScript language program. Refer to “Fax Parameters” on page 29 for further information about FaxOptions defaults and the keys found in this dictionary”

Google tells me this is what you needed in your PostScript file to send a fax:

  <<
    /OutputDevice /Fax
    /FaxOptions <<
      /DialCallee (555-0199)
    >>
  >> setpagedevice