Fritzbox 7340 Dect incoming false call signals

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mruane

420 posts

Ultimate Geek

#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

4962 posts

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Inactive user

#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.

kornflake

409 posts

Ultimate Geek

#737508 26-Dec-2012 21:53

delayed/broken sip signalling?

richms

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#737518 26-Dec-2012 22:19

Not happened for me, and I have several italk and 2talk lines configured on my fritzbox

Richard rich.ms

mruane

420 posts

Ultimate Geek

#737529 26-Dec-2012 23:27

So, would you say a reload of the latest firmware would be the next most useful step?

Cheers Mike

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