>> Can anyone enlighten me further into how this would be >> done and if such back doors exist in other operating >> systems. > > That was most likely DEC's intent with the "field:service" account. No, that is so the field circus guy has an account to run diagnostics and get error logs from. But it was the intent of the conversational boot and UAFALTERNATE hack. I've never seen a system that can't be entered without a password if you have unrestricted physical access to the hardware.