TM> HOw does this work?  I was reading about it in the new episode of Time
 TM> Digital and they were talking about a # that is stored in the service
When the user presses "send" the switch "challenges" the request by sending
the phone a small piece of data which is related to the phone number and
(supposed) ESN of the phone.  A small software program running in the phone's
firmware takes the data presented to it by the switch, runs it through the
 algorithm software program for that particular phone's
manufacturer, and spits out a small "response" message to the switch.  If
the switch agrees with the phones response, the call goes through-if not,
the phone is a clone and gets a big nothing as well as the carrier being
notified that the number has been cloned.
Each call attempt results in a completely different "challenge" message.
The whole process is buried in the software of the switch and the firmware
of the phone.  No special programming of the phone or switch is necessary.
The switch knows the particular algorithm to use because each ESN identifies
the manufacturer of the phone.
Pretty slick, eh?
There's just one small problem.  Older phones have no knowledge of such a
system.  Thus, this wonderful fraud prevention system only works with the
newest phones-and then often only with "top of the line" phones.  So if you
clone an old clunker, you still can make calls for free even if the carrier
is touting this wonderful innovation...
... Do cellular phones promote reckless dialing?
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