Block anonymous calls

Discussion in '3CX Phone System - General' started by complex1, Jul 31, 2014.

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  1. complex1

    complex1 Active Member

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    Hi,

    I know this is a very basic knowledge of the 3CX system and I should know the answer to it, but I don’t.

    How to block or redirect anonymous incoming phone calls with an empty caller ID.
    I have tried “Anonymous”, “(none)”, “unavailable”, “000*” in the extension exceptions tab but none of them activate the rule and redirect the call.
    What should I fill-in to redirect these anonymous calls?

    Thank you.
     
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  2. leejor

    leejor Well-Known Member

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    Things may work differently with various types of caller ID.
    Did you come across this? http://www.3cx.com/blog/docs/trap-and-block-anonymous-callers/
     
  3. neilhooper

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    I don't know if this would work as we don't have these type of calls.

    Try reformatting the incoming call e.g. ( ) > 1234567890 There's a space in between the brackets.

    Then set up an incoming rule to trap 1234567890 and end the call or add 1234567890 to the blacklist.

    I don't know whether the flow through the system would allow it to work.

    As I say, I don't know if this would work but it may worth a go.

    - Neil
     
  4. leejor

    leejor Well-Known Member

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    Trying to block withheld numbers relies on your provider sending something specific that can be acted upon. In North America, for example, call display devices will display (generally) Out of Area (no number was sent), Blocked Call (caller is deliberately blocking their name/number), or even in some cases Long Distance (the call is coming in from a long distance trunk group.

    However, the entire phrase is not sent in most cases, it could be, but CID devices only require a single letter to trigger the correct phrase, which is a Bellcore standard. I have not looked into how it is handled in areas that do not use the same standard, and most others are incapable of sending alpha characters.

    Converting no number sent to a pseudo number with the intent to block,(unless you have confirmed that this is what you wish to do), may end up blocking legitimate calls that originate from an area where number cannot be sent (older switching equipment/ emergency call passed through an operator).
    No number, and a deliberately blocked number, can be two completely different animals.
     
  5. complex1

    complex1 Active Member

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    Hi guys,

    Thank you for your reply.

    This is what I have done to check but all without any success.
    1. I have setup Block “Anonymous” Callers as described in http://www.3cx.com/blog/docs/trap-and-block-anonymous-callers/
    2. Reformatted the incoming call as suggested by neil into “( ) > 1234567890”
    3. Redirect Caller ID “Anonymous” to “End Call” at the Extension Exceptions tab

    With my cell phone I dialled my phone number and using number suppression.
    The desk phone is ringing with the caller ID “Anonymous”
    In 3CX I checked this incoming call.
    The Caller ID is empty, no spaces, no blanks, no numbers, no text like “Anonymous”, no nothing.

    In the Server Activity Log I see:
    [Flow] Looking for inbound target: called=3122366xxxx; caller="Anonymous" <sip:mad::5060>
    CallerNameAddr: "Anonymous"sip:;nf=e

    And in the From field in the incoming INVITE
    From: "Anonymous"<sip:91.195.160.2>;tag=6puqt5dt45pczyni.o
    And not
    From: "Anonymous"<sip:Anonymous@91.195.160.2>;tag=6puqt5dt45pczyni.o

    Somehow 3CX generates “Anonymous” but you can do nothing with it.

    Thank you.
     
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  6. leejor

    leejor Well-Known Member

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    I would suspect that (Anonymous)is generated by 3CX when there is simply no number received, it would seem that in the UK there is no differentiation in a suppressed (blocked) number, and one where no number is sent from the originator, unlike Bellcore.
    In most cases, a number would be available, so other than a couple of examples that I mentioned earlier, you can probably assume that no number = blocked.

    Are you using a VoIP provider, or a gateway? If a gateway, there may be an option to insert a number if none is received. Other than that, you might contact your provider to see if some sort of digit string could be sent, rather than nothing.
     
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