Fritzbox 7340 Dect incoming false call signals

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mruane

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#112891 26-Dec-2012 11:46

Hi all

Has anyone come up against an issue I have with the Fritzbox 7340 and DECT, which reports that incoming calls are being received that simply did not happen!

ABout once an hour, my Missed Call log reports that I have missed a call from "Unknown" that I know for sure never happened. Clearly this must be a transient signal being developed in the device and I wondered in anyone else has experienced this and resolved it.

My Fritzbox does not have a Landline connection for phone and all calls are handled by VOIP. Currently the Landline phone connection port is not used. The only "Own Telephone Number" that I have defined is to an Asterisk box, and i have confirmed that the bogus calls signals did not originate from Asterisk.

So far, the only way around this is to create a Call Block rule to ignore calls that have no Caller ID, which is a bit draconian. Does anyone have any other ideas about how to squash the false call signals that keep appearing in the Missed Call log?

Cheers Mike

sbiddle

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#737325 26-Dec-2012 12:17

My pick would be a bot running a SIP script attack against the device.

I'm not actually sure what protection against this the Fritz!box has, I should have a play over the next few days.

mruane

420 posts

Ultimate Geek

#737331 26-Dec-2012 12:27

I have observed this behaviour right from the first day I installed this Fritzbox and prior to creating any Local Numbers at all, my impression was that it had to be a local transient signal. It was the one reason that I did not enable the DECT base station originally. Now I see the benefits of the DECT base, and I wanted to leverage it.

So yes it could be a Bot although the one SIP connection I now have is internal i.e. the one connection is to my local ATCOM IP02 PBX rather to an external SIP provider.

I guess if the Missed Call log on your Fritzbox is not generating heaps of call records from an "Unknown" caller then I must have a suspect box!

Cheers Mike

sbiddle

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#737350 26-Dec-2012 12:53

You don't need to have a SIP registration for a bot to me scanning your system, you merely need port 5060 to be exposed to the internet.

Bots are a massive problem these days, and are the reason why you should never ever have a port forward on port 5060 unless you fully understand the security risks of doing so. I've heard of plenty of people using the likes of 2talk, setting a port forward on their router to an SPA and then finding their phone continually giving one right as the bot script hits their ATA.

I picked up a 7390 and fritz!fon while in Aussie in August and have used it for all of an hour, I really need to have a play witrh it again before I sell it.

chevrolux

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#737488 26-Dec-2012 21:00

Does sound a lot like a bot attack.

The Frtitz will intercept all packets on 5060. But I wouldn't have thought anonymous calls would be passed on to the extensions. Havent done any captures to see what exactly is going on though to confirm anything.