How to handle harassing anonymous calls with blocked caller ID


We have a location who is receiving harassing calls daily from someone who is masking their caller ID. We suspect the person is an ex-employee because he knows names of current employees.

Our system has 8 analog lines from the telco that are by default sent into an IVR that then routes the calls to 1 of 2 portions of the business.

Our LEC has a call tracing feature, but I don’t think it will work because I can’t guarantee that our internal users will get the same analog line when attempting to call *57 after a harassing call.

Do any of you have any creative ideas to how we can either get the call trace to work correctly so the LEC and police can do their part or how to unmask the caller ID? I saw the details of Mitnick’s plan using a cloud SIP provider to do this, but I don’t think I can apply this to our situation without converting our calls to a SIP provider.

In the past we have created a separate inbound route and send the calls to 1 extension (manager’s extension) but this is not going to stop the problem. We do not wish to entirely block the unknown callers so we do not lose legit calls with no caller ID.

Any ideas?

Thank you for reading.


I think you are approaching this in the wrong manner.
Simply get the person receiving the calls to note down the time/date of the calls. Review the logs of the PBX, and match the calls to the time it actually initially hit your system, then send those details, along with the details of the calls to the police.
They will contact the LEC, and request them to provide the ANI of the call to your system, at the times specified.
Cue a visit from the boys in blue, and you might find the call nastiness ceases.
It is important that you are very accurate in providing the correct time to the police, as they will not be able to double check the results they get back.

As an interesting, but completely irrelevant note, some systems used to allow you to ignore the Call ID Privacy flag, allowing you to see the originating number, though nothing at SMB level (ie Nortel DMS100).

After you send the details to the police, the next thing that will happen is… nothing.

You are on your own to resolve this.

I personally have not used this website, but it is in my notes, you may give it a try:

I would be interested in hearing how things work out.

Interesting… It works by forwarding the call to a toll free number, which then allows them to extract the info. Would it be possible to forward to ones own toll free number? For example, with asterisk and a SIP trunk provider, would it be possible to have asterisk forward the calls to a 800 number trunk which would then contain the info and be displayed?

I had the same idea years ago, never tried it though. In my situation, it is no longer necessary. I use a system I refer to as “reverse harrassment”. My system does a real-time lookup to see if the caller is a telemarketer, then directs them to a module that talks nonsense with them and keeps them on the line as long as possible, to waste their time. Anyone blocking their number cannot be my friend, and is automatically dumped to same queue.

It’s a laugh a minute, and we look forward to annoying callers! (they are recorded to emailed to us as MP3’s)