Slashdot Mirror
Foiling 'Backdoor' Voicemail Spam?
Cheffo Jeffo 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)?"
Do the spam messages occur at regular intervals? You could try turning your voice mail box off for an hour/day/week. The idea being that they call, find no box, and delete your number from the list.
Starting the message with a "disconnected" tone or somesuch might help. This might not work though - if they're using a computer with ISDN technology, the card gets told digitally when the call is disconnected (or rerouted etc).
Have you registered a complaint with your telephone company (mobile provider or whatever)? Even if they refuse to do something, make sure they get a complaint - written is usually best. If enough customers complain about something they will look into it. Find out if their competitors are willing to help, and if they are mention it in your letter. The prospect of losing a customer to a competitor will carry more weight!
-- Steve
1) The telco is providing this dubious backdoor service
2) The service is costing you money
3) complain to the telco, threaten to swap services (if you can)
Note, in australia I would complain to the TIO, as this costs the telco money either way.
4) ???
5) PROFIT
09F91102 no, 455FE104 nope, F190A1E8 uh-uh, 7A5F8A09 that's not it, C87294CE no. Ah! 452F6E403CDF10714E41DFAA257D313F.
Spammers assume that if you don't like their message, you'll simply delete it. Only a tiny fraction of recipients ever actually respond, and most of those responses are for placing orders. This means they can employ a very small number of customer service reps, making spam very cost-effective. The reason it works is that you, the victim, simply delete the spam and take no action.
To force spammers into finding a better way to conduct business, we must tip the balance of costs. If every victim called them up and wasted 5 minutes of the spammer's time, the ratio of sales to non-sales would become pretty thin, pretty quick. Their costs for paying phone-monkeys would quickly surpass penis pill profits.
It's even better if they have a toll free number you can call, because it's their dime. (Beware of ANI, don't counterharass them from your own phone!) It actually costs them extra if you call them from a payphone, hint hint. I got answering-machine-spammed a while ago, and it turns out that 800 470 0865 is also answered by a machine. There's a voicemail system behind it, and it's possible to tie up the line indefinitely just by pushing 1(wait)*(wait)1(wait)*(wait)....
If they have a website you can visit, well, I'm sure you can figure out what to do. Evil blackhats of the world, unite and make the world a better place! If spammers' hosting costs skyrocket, they might see the light.
Place an order! Then cancel it. Document both. Keep CLOSE TRACK of your CC bills! If they charge you anyway, reverse the charges. (That costs them BIG, and if it happens too often, they'll get their merchant account canceled.)
It only takes a small percentage of spam victims, pissed off and ready to take action, to impact the spammers' bottom lines. You probably spend at least 5 minutes a day sorting through spam email, listening to junk voicemail, and throwing out the dead-tree junk that lands in your mailbox. Spend 5 minutes a day fighting back.
FWIW -- I recorded the message that you get when you use the backdoor and enter an invalid mailbox number (I used a mailbox that differed from mine only in the last digit) and used that as my mailbox identifier (the announcement that you get when you use the backdoor and enter my mailbox number).
...
It's been 24 hours and no voicemail spam as yet
All you have to do is get your phone number listed under the maiden name of yourself (if you're female and married) or the maiden name of your wife/mother as appropriate. Then whenever anyone calls for that name you know it's a phone spam and you can legitimately tell them there's nobody there by that name and hang up.