asks: "After receiving a number of (repeated and irritating) voicemail spams in the past week, I starting investigating what my options were for blocking these pre-recorded messages that are eating up my mailbox and costing me money when I check my messages using a cellphone. While it appears that I can do nothing at this point in time (I am Canadian and the CRTC hasn't had the wisdom to make this stupidity illegal yet), I was wondering if there is a technical measure that I can use to stop the insanity (other than reverting to a regular answering machine).
In my particular case, the telemousketeer autodialer dials into the telco's voicemail backdoor (xxx-210-0yyy) and punches in the phone number xxx-yyy-zzzz. If they find that there is no mailbox, then they hang up and remove the number from the call list. Otherwise, they leave their obnoxious solicitation.How do they determine whether a mailbox exists (as you can tell, I am no expert)?"
Might there be some tone that you can record at the start of the outgoing message that will fool the autodialer into marking the number as "disconnected"?
"If I were to record the 'I'm sorry, <some-phony-number> is not a valid mailbox, please try again' message as my mailbox identifier, would that work?
Any other ideas (other than the providing Slashdot with the URLs for the offending companies to punish their web servers)?"