[Asterisk-Users] Validating a phone number

[trixter http://www.0xdecafbad.com]

On Sun, 2005-07-17 at 00:01 -0700, Peter Hsu wrote:
> I'm concerned about people dialing out of our asterisk server to numbers 
> they shouldn't be dialing.
> 
> Is there a concrete algorithm for determining whether a phone number is 
> "normal".  i.e. calling this phone number would result in a normal long 
> distance rate.
> 
> It seems like the pattern 1NXXNXXXXXX for the U.S. is fairly commonly used, 
> but it wouldn't catch erroneous phone numbers such as "1411XXXXXXX" (and the 
> other X11 numbers)
> 

normally those dont work with a 1 before them, but I cant say that is a
guarantee with all providers.

19xx is normally premium service and has a sometimes steep charge.
1700xxx is another number that normally places a higher than normal
charge to callers for calling.

In america there are some numbers that appear normal but are premium
service numbers, there are some in NJ that charge $5 to call in the 201
area code but they can exist in other states as well.

You may want to filter numbers that would fit the 1NXX... format but
arent in the US or Canada either.  There was a company that had a
number )I forget where somewhere in the caribean) that was part of the
NANPA (ie 1NXX) but charged $2511/minute to callers.  Because they are
not in the US the FTC rules about declaring that it is a premium service
number and the charges when first called do not apply.  There are only a
couple area codes 809 seems to come to mind but I cant guarantee that.

In short you might investigate a phone company service blocker for
premium service numbers and try your best to block what you can but it
would be impossible for someone without SS7 network access to see what
the rate of the call is since these numbers can hide virtually anywhere.


> I tried googling this topic, but it's hard to find anything with such common 
> keywords.  If anyone can direct me to a good resource, I'd appreciate it as 
> well.
> 
NANPA manages all the numbers in the north american numbering plan, if
memory serves their page is nanpa.org and they used to have rate center
information available on their page for free that you can download (and
you would need to parse it and continually get updates as new exchanges
are allocated).


> On athe same topic, I'm worried about area codes like 809.  Are there any 
> other such area codes that should be avoided?
> 

Ahh glad you brought that up, see above.  I think there are a couple of
them, but I dont know off hand what they are..  try googling 'toll fraud
809' and see if that works.

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
UK +44 870 340 4605   Germany +49 801 777 555 3402
US +1 360 207 0479 or +1 516 687 5200
FreeWorldDialup: 635378
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