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Silent calls from 100

zpeterk
Grafter
Posts: 377
Registered: 14-04-2007

Silent calls from 100

I am getting 10-20 silent calls over a day from a number displayed as 100. Is there anything that can be done to block them?
20 REPLIES
Community Veteran
Posts: 3,380
Thanks: 2
Registered: 18-01-2013

Re: Silent calls from 100

paxy
Grafter
Posts: 253
Registered: 01-08-2007

Re: Silent calls from 100

I have been getting the same - sometimes in the middle of the night.  I think the calls are coming direct through SIP rather than through the telephone network.
I did lots of googling and eventually seem to have resolved it but changing away form using port 5060.  Since making the change I have had none.
Community Veteran
Posts: 3,380
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Registered: 18-01-2013

Re: Silent calls from 100

Oops - I missed the bit where this was in the VOIP forums and assumed it was a normal landline.
Ignore the above post from me  Lips are sealed
Community Veteran
Posts: 5,360
Thanks: 188
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Registered: 11-08-2007

Re: Silent calls from 100

Have you got Plusnet or Gradwell VoIP ?,  as the number "100" is Gradwell customer services   Shocked
See attachment below -
Community Veteran
Posts: 3,380
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Registered: 18-01-2013

Re: Silent calls from 100

As paxy says - changing the port from 5060 to a non standard port should do the trick. According to the post linked below, the "100" calls are hackers trying to find a way into PABX systems. Makes for interesting reading :
http://www.dslreports.com/forum/r28035253-Receiving-calls-from-name-number-100-that-don-t-get-logged
zpeterk
Grafter
Posts: 377
Registered: 14-04-2007

Re: Silent calls from 100

We must of had at least 50 today, I have the VOIP on a time switch so at night it is quiet.
How does changing the port stop the calls?
Community Veteran
Posts: 3,380
Thanks: 2
Registered: 18-01-2013

Re: Silent calls from 100

Did you read the link I posted above ? Quite a good description of what is going on in that thread.
Basically the hackers/scammers go through a range of IP addresses and probe port 5060 on those addresses for possible hackable PABX systems. By changing it to a number other than port 5060 which 99% of VOIP services run on, they will (hopefully) skip your IP rather than investigate further.
Of course, if everyone changed their ports from 5060, the hackers would then have to spend more time and do a full port scan / probe on ever IP address to try and find the PABX / VOIP but for the moment, changing it will generally deter them.
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Silent calls from 100

Are you using the outbound proxy ?
From what I can see, using that ought to prevent this from happening since there are no ports forwarded on the router. With the o/b proxy you have a NAT session directly
to the proxy and so any sip traffic will only be allowed if it comes from the proxy.
zpeterk
Grafter
Posts: 377
Registered: 14-04-2007

Re: Silent calls from 100

Hello
I am using outbound proxy and I also have 1060 forwarded to my Zoom voip box, do I therefore need to remove the rule forwarding the 1060 port?
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Silent calls from 100

You shouldn't need any port forwarding when using the outbound proxy.
zpeterk
Grafter
Posts: 377
Registered: 14-04-2007

Re: Silent calls from 100

I have removed the port 1060 redirect and sent it to no where ( ie an unattended ip address) and the phone is still ringing all the time.
Help
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Silent calls from 100

I'm pretty sure this isn't attributable to port scanning. My phone rang at close to midnight last night and there was no call registered.
When you're using the outbound proxy, there's a permanent connection to the server via a NAT session through your router firewall. This will only allow incoming traffic from the server IP.
I've checked the firewall on my router and there are ( as expected ) no ports open so I don't see how this call is coming directly to my sip device.
That's not to say that someone isn't calling my sip id ( or allocated phone no ) and the call is being routed via the server, but that doesn't explain why it's not logged.
I'm going to try some direct sip->sip calls later if I get time to see if they are logged...
zpeterk
Grafter
Posts: 377
Registered: 14-04-2007

Re: Silent calls from 100

I have found a duplicated rule in the list and deleted it the phone is now silent, thanks for your help
Community Veteran
Posts: 6,249
Thanks: 428
Fixes: 39
Registered: 30-07-2007

Re: Silent calls from 100

Glad it's sorted. Hopefully my call the other night was a one off and nothing to do with these silent calls.