full-disclosure - Re: Static Injection into Commercial Lines - DoS on Vonage

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Message-ID: <47EA0B0A.9030505@ub.uni-tuebingen.de>
Date: Wed, 26 Mar 2008 09:36:26 +0100
From: Anja Hofmann <anja.hofmann@...uni-tuebingen.de>
To: Jan Clairmont <janclairmont@...oo.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Static Injection into Commercial Lines - DoS
 on	Vonage - Current Status

Hi!
Jan Clairmont wrote:
> I have received calls and the caller is  injected with a sound similar to a fax modem static. Now my outbound callers hear static.  This is obviously a problem either with Comcasts injecting noise packets or Verizon or a carrier that carries the VOIP call.  This is prevalent with others who subscribe to your service.
>   
 From my experiences with audio recording/speech processing and internet 
telephone applications, there can be a lot of reasons for static apart 
from DoS attacks.
First I would check whether your computer and its audio equipment are 
working properly:
- Do you use simple headsets for making calls? (cheap headsets = bad 
audio quality)
- Are any mobile phones or other wireless devices near your computer 
which could cause interferences?
- Do you have any other applications running in the background that 
access your sound card?
    (For example turning down  internet radio  / mp3 clients while 
making a phone call?)
Concerning your ISP, some ISPs ban P2P applications and some VoIP 
clients are P2P-based. So I would check whether there have been any 
changes to the Terms of Service recently.
Here are some links I found while searching for "VoIP trouble shoot":
http://www.pingplotter.com/tutorial/VoipTroubleshooting.html
http://www.voip-info.org/wiki/view/How+To+Debug+and+Troubleshoot+VOIP
http://voipreview.org/Forum/thread/130.aspx
Have a nice day!
Yours sincerely,
Anja Hofmann

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