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Standard User electricblu
(newbie) Mon 18-Dec-17 18:19:16
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Ghost call woes, please help!

[link to this post]

We have recently got a VOIP phone for our home based business and are having some terrible trouble.

We keep getting constant calls from '1001' or 'test' or '2000001' and other iterations like these.

Some research has led me to believe these are called 'ghost calls'. I have spoken to my VOIP provider about this who advised that it is due to the ISP sending packets of data to my connection.

He also advised that I needed to speak with my ISP (Vodafone obviously) and they would, and I quote:
"You will need to contact them and explain that you’re using a VoIP service – They can then change the broadband operation onto a different channel within the settings of the router which will solve the issue."

Now I questioned this a little further to try and find out what these 'channels' were. He was insistant, that if I phoned vodafone techincal support and explained what I had to him that they would solve the issue.

I did try and speak to Vodafone who said they had no idea what he was talking about other than WIFI channels, which are obviously not going to solve the problem.

When I went back to my VOIP provider, the guy emailed back with the following:

"This is shocking – A VoIP provider wouldn’t know what channels ISP’s use. Each ISP have completely different set ups. It would be impossible for us to know what channel each ISP needs to use to prevent ghost calls.

I would suggest putting them onto a 3 way conference call with you and myself. I don’t know what else to suggest. Your ISP is causing it and should be able to resolve it. I’ve never once come across and ISP that doesn’t know how to stop the ghost calls on a VoIP service or what channel they need to switch the broadband operation to – Shocking!"

So I'm basically stuck. Our VOIP phone is all but unusable due to the (literally hundreds of) ghost calls we keep receiving. Does anyone know if this guy knows what he is talking about? Is there some magic switch at Vodafones side that can resolve this problem or else is there anything I can do at my end?


Kind regards

Standard User clyde123
(regular) Mon 18-Dec-17 20:31:40
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Re: Ghost call woes, please help!

[re: electricblu] [link to this post]
I really can't give an answer to your question, but here's some info on Voip ghost calls.
Hopefully this might be of some help.
Standard User ferretuk
(member) Mon 18-Dec-17 21:52:30
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Re: Ghost call woes, please help!

[re: electricblu] [link to this post]
The explanation from your VOIP provider sounds like nonsense to me. What are the 'channels' that they refer to? ISP's don't use 'channels'.- They route traffic to and from your IP address.

Does your VOIP provider provide call records? Do they list incoming calls? Assuming they do, and these calls don't appear on them then something is making a direct SIP call to your phone. Is it on a public IP address or behind a NAT router? If the latter, have you forwarded port 5060 to the phone? Try removing the port forward and/or add a rule to block access to the port from the WAN.

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Standard User ukhardy07
(knowledge is power) Tue 19-Dec-17 00:47:34
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Re: Ghost call woes, please help!

[re: electricblu] [link to this post]
I do security testing at large scale clients and it is common for things like port and vulnerability scans against VOIP phones to cause these ghost calls. With your phone likely being directly internet facing, it is possibly being port scanned. These types of scans happen both automatically, but also can be the sign of someone targeting your device directly e.g. trying to find vulnerabilities on it or something similar.

Any device which is not behind a firewall should be considered a security risk.

VOIP Phones need to be purchased from a reputable vendor who provides ongoing firmware updates, these need to be applied ongoing.

Clients (large scale businesses) do not have this problem internally due to well defined firewall rulesets and they perform firmware upgrades by subscribing to vendor notifications.

I personally think Vodafone can do nothing and this idea of channels is nonsense.

Edited by ukhardy07 (Tue 19-Dec-17 00:49:27)

Standard User ian72
(eat-sleep-adslguide) Tue 19-Dec-17 08:40:27
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Re: Ghost call woes, please help!

[re: electricblu] [link to this post]
Is the phone on the internal side of the firewall using port forwarding or is it directly on the Internet? If it is direct then depending on ports required it may be better to move it internally and just forward the ports it needs and that might close down the problem. You may also be able to set rules on the router/firewall to only allow connections from your VoIP providers server IPs (assuming that your VoIP calls are coming via a gateway). Alternatively if the VoIP provider can specify the source and port requirements then Vodafone may be able to close them down at their end (although Vodafone aren't necessarily going to be in the top tier of providers for that sort of specific technical configuration/support).

The VoIP provider does appear to be talking gibberish - if they were talking about ports rather than channels it would make a lot more sense. As others have said talking about channels in an IP network is nonsense.
Standard User johnwigley
(newbie) Tue 19-Dec-17 12:18:30
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Re: Ghost call woes, please help!

[re: electricblu] [link to this post]
This will be solvable, can you please describe your exact configuration:

1) who your voip provider is?
2) what equipment you're using, ie phone make model, router etc?
3) I assume you're connected with a phone to the provider, without your own voip pbx setup locally?
4) the config details you're using in the phone EXCEPT the username and password, so the SIP server, and the connection protocol UDP, TCP, or TLS?
5) Have you configured any port forwarding rules on your router/firewall for this voip connection or any other reason?
6) Is UPNP enabled on the router? If so, do you need it for anything you're aware of?

The reason for all these questions, is that fundamentally the ghost calls could either be coming in through your voip provider because they allow inbound SIP calls direct to their proxy, or else could be coming in via your own connection because either you, your router, or your phone has explicitly opened an inbound connection path. You need to be able to identify WHERE they're coming from in order to stop them.
Standard User Michael_Chare
(fountain of knowledge) Sat 23-Dec-17 16:36:50
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Re: Ghost call woes, please help!

[re: clyde123] [link to this post]
I have Vodafone broadband, a Zyxel VMG8924-B10A router and a Gigaset N300 connected to Sipgate. I don't have your problems.

Michael Chare
Standard User DigitalDaz
(newbie) Sun 25-Feb-18 23:39:34
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Re: Ghost call woes, please help!

[re: Michael_Chare] [link to this post]
We come across this quite frequently and it is just the hackers scanning.

I'm not familiar with your particular handset but what is very likely happening is that because you are registering to your provider there is a NAT tunnel open and this is what they are hitting on,

In most cases where we see that what is happening is you have your transport protocol set to UDP and your phone will be listening on a port at or around 5060.

A very quick fix usually is to switch the transport protocol to TCP if your provider supports it, most providers do nowadays.

If that is not an option many sip phones have some sort of setting to block any other traffic that does not come from the sip provider they are registered to.

Hope this helps, I know the pain of that.

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